Proteolysis is the directed degradation digestion of protein s by cellular enzyme s called protease s or by intramolecular digestion. Purposes Proteolysis is used by the cell for several purposes. They include Removal of N terminal methionine residues after translation biology translation . Removal of the signal peptide signal sequence of peptides after their transport through a cell membrane membrane Separation of virus biology viral proteins that were translated from a polycistronic mRNA Digestion of proteins from foods as a source of amino acid s Conversion of predecessor proteins proenzyme s, zymogen s, prehormone s into their final structures. Degradation of unneeded or damaged proteins for example cyclins at different stages of the cell cycle . Proteolysis is also used in research and diagnostic applications In gel digestion of proteins after separation by gel electrophoresis for the identification by mass spectrometry . Digestion of proteins in solution for proteomics proteome analysis by liquid chromatography mass spectrometry LC MS . Examples Examples of serine proteases include trypsin chymotrypsin elastase papain Venoms Certain types of venom, such as those produced by venomous snake s, can also cause proteolysis. These venoms are, in fact, complex digestive fluids that begin their work outside of the body. Proteolytic venoms cause a wide range of toxic effects, ref name Hayes WK. 2005. http www.llu.edu llu grad natsci hayes research c venom.html?PHPSESSID 55842bf3eeb83dcdfec66c45b91925fc Research on Biological Roles and Variation of Snake Venoms. Loma Linda University. ref including effects that are Cytotoxin cytotoxic cell destroying Hemotoxin hemotoxic blood destroying Myotoxin myotoxic muscle destroying Hemorrhage hemorrhagic bleeding See also The Proteolysis ... In gel digestion References references External links eMedicineDictionary Proteolysis http www.proteolysis.org Proteolysis MAP from Center on Proteolytic Pathways Protein posttranslational modification ... more details
Image PMAP logoV8 2blue.png 100px thumb right PMAP logo The Proteolysis MAP PMAP is an integrated web resource focused on protease s. ref Igarashi Y, Heureux E, Doctor KS, Talwar P, Gramatikova S, Gramatikoff K, Zhang Y, Blinov M, Ibragimova SS, Boyd S, Ratnikov B, Cieplak P, Godzik A, Smith JW, Osterman AL, Eroshkin AM. PMAP databases for analyzing proteolytic events and pathways. Nucleic Acids Research . 2008 Oct 8. Epub ahead of print ref Rationale PMAP is to aid the protease researchers in reasoning about proteolytic neural network networks and metabolic pathways . History and funding PMAP was originally created at the Burnham Institute for Medical Research , La Jolla, California. In 2004 the National Institutes of Health NIH selected a team led by Jeffrey W. Smith , to establish the Center on Proteolytic Pathways CPP . As part of the NIH Roadmap for Biomedical research, the center develops technology to study the behavior of proteins and to disburse that knowledge to the scientific community at large. Focal point Proteases are a class of enzymes that regulate much of what happens in the human body , both inside the Cell biology cell and out, by cleaving peptide bonds in proteins . Through this activity, they govern the four essential cell functions differentiation cellular differentiation , motility , division and cell death and activate important extracellular episodes, such as the biochemical cascade effect in blood clotting . Simply stated, life could not exist without them. Extensive on line classification system for proteases also referred as peptidases is deposited in the MEROPS database. The goal Proteolytic pathways, or proteolysis, are the series of events controlled by proteases that occur in response to specific stimuli. In addition to the clotting of blood ... Official website http www.burnham.org Host institution website http cutdb.burnham.org Proteolysis ... http www.protease.org International Proteolysis Society http merops.sanger.ac.uk Merops the peptidase ... more details
Orphan date February 2009 Heavy meromyosin HMM is the larger of the two fragments obtained from the muscle protein myosin II following limited proteolysis by trypsin or chymotrypsin . HMM is used to determine the polarity of actin filaments by decorating them with HMM then viewing them under the electron microscope . References http www.answers.com topic heavy meromyosin?cat technology Category Motor proteins biochem stub ... more details
Metalloproteinases or metalloproteases constitute a family of enzyme s from the group of protease s, classified by the nature of the most prominent functional group in their active site . These are proteolysis proteolytic enzymes whose catalytic mechanism involves a metal. Most metalloproteases are zinc dependent, some use cobalt . The metal ion is coordinated to the protein via three ligands . The ligands co ordinating the metal ion can vary with histidine , glutamate , aspartate , lysine and arginine all possible ligands. The fourth coordination position is taken up by a labile water molecule. There are two subgroups of metalloproteinases exopeptidase s metalloexopeptidase s EC number 3.4.17 . endopeptidase s metalloendopeptidase s 3.4.24 . Well known metalloendopeptidases include ADAM protein s and matrix metalloproteinase s. Treatment with chelating agent s such as EDTA leads to complete inactivation. EDTA is a metal chelator which removes zinc, which is essential for activity. They are also inhibited by the chelator orthophenanthroline . External links The MEROPS online database for peptidases and their inhibitors http merops.sanger.ac.uk cgi bin family index?type P M Metallo Peptidases MeshName Metalloproteases eMedicineDictionary Metalloproteinase Proteopedia http proteopedia.org wiki index.php Metalloproteases Metalloproteases See also The Proteolysis Map Category EC 3.4.24 Category EC 3.4.17 hydrolase stub Proteases de Metalloproteasen fr M talloprot inase id Metaloprotease he nl Metalloprotease pt Metaloprotease ... more details
protein Name caspase 4, apoptosis related cysteine peptidase caption image width 240px HGNCid 1505 Symbol CASP4 AltSymbols ICE rel II, ICH 2, TX EntrezGene 837 OMIM 602664 RefSeq NM 001225 UniProt P49662 PDB ECnumber 3.4.22.57 Chromosome 11 Arm q Band 22.2 q22.3 LocusSupplementaryData Caspase 4 is an enzyme that proteolysis proteolytically cleaves other proteins at an aspartic acid residue, and belongs to a family of cysteine protease s called caspase s. The function of caspase 4 is not fully known, but it is believed to be an inflammatory caspase, along with caspase 1 , caspase 5 and the murine homology biology homolog caspase 11 , with a role in the immune system . ref cite journal author Martinon F, Tschopp J title Inflammatory caspases and inflammasomes master switches of inflammation journal Cell Death Differ. volume 14 issue 1 pages 10 22 year 2007 pmid 16977329 doi 10.1038 sj.cdd.4402038 ref See also The Proteolysis Map References references External links The MEROPS online database for peptidases and their inhibitors http merops.sanger.ac.uk cgi bin merops.cgi?id C14.007 C14.007 Cysteine proteases Category Enzymes Category Caspases gene 11 stub ... more details
protein Name caspase 5, apoptosis related cysteine peptidase caption image width 240px HGNCid 1506 Symbol CASP5 AltSymbols ICE rel III, ICH3 EntrezGene 838 OMIM 602665 RefSeq NM 004347 UniProt P51878 PDB ECnumber 3.4.22.58 Chromosome 11 Arm q Band 22.2 q22.3 LocusSupplementaryData Caspase 5 is an enzyme that proteolysis proteolytically cleaves other proteins at an aspartic acid residue, and belongs to a family of cysteine protease s called caspase s. It is an inflammatory caspase, along with caspase 1 , caspase 4 and the murine caspase 4 homology biology homolog caspase 11 , and has a role in the immune system . ref cite journal author Martinon F, Tschopp J title Inflammatory caspases and inflammasomes master switches of inflammation journal Cell Death Differ. volume 14 issue 1 pages 10 22 year 2007 pmid 16977329 doi 10.1038 sj.cdd.4402038 ref See also The Proteolysis Map References references External links The MEROPS online database for peptidases and their inhibitors http merops.sanger.ac.uk cgi bin merops.cgi?id C14.008 C14.008 Cysteine proteases Category Enzymes gene 11 stub ... more details
Jeffrey W. Smith is Director , Program for Excellence in Nanotechnology , Center on Proteolytic Pathways, ref Smith JW. Allostery and proteolysis two novel modes of regulating integrin function. Matrix Biol. 1997 Oct 16 4 173 8. Review. ref Tumor Microenvironment at of the Burnham Institute . Jeff earned his Ph.D. in biological sciences at UC Irvine in 1987. Following postdoctoral training at The Scripps Research Institute , he was appointed to their staff in 1991. Dr. Smith was recruited to The Burnham Institute in 1995. See also Nanotechnology The Proteolysis Map References reflist External links http www.burnham.org default.asp?contentID 205 Burnham Institute for Medical Research Jeffrey W. Smith Faculty page http www.ncbi.nlm.nih.gov sites entrez?db pubmed&cmd DetailsSearch&term smith jw and protease&log activity Jeffrey W. Smith, Selected list of publications via PubMed, NIH National Library of Medicine Persondata Metadata see Wikipedia Persondata . NAME Smith, Jeffrey W. ALTERNATIVE NAMES SHORT DESCRIPTION DATE OF BIRTH PLACE OF BIRTH DATE OF DEATH PLACE OF DEATH DEFAULTSORT Smith, Jeffrey W. Category The Scripps Research Institute Category Living people med bio stub ... more details
Orphan date February 2009 Expert subject Molecular and Cellular Biology date February 2009 Unreferenced date February 2009 An antigenic determinant is the molecular aspect or moiety of a molecule that lets an antibody complement it and thus by definition, makes the molecule an antigen classified further, an immunogen within an organism . A Protein can underlie further modification within a biochemical pathway such as glycosylation, phosphorylation or proteolysis. This, by altering the structure of the protein, can produce new epitope s which are called neoantigenic determinants as they give rise to new lat. neo antigenic determinants and require separate, specific antibodies for recognition. References reflist Category Immune system molecular cell biology stub ... more details
Summary Information Description trans Translation stages A through F. A ribosome with its RNA binding sites, designated E, P, and A, is stuck near the 3 end of a broken mRNA. The tmRNP binds to the A site, allowing the ribosome to switch templates from the broken message onto the open reading frame of the tmRNA via the resume codon blue GCA . Regular translation eventually resumes. Upon reaching the tmRNA stop codon red UAA , a hybrid protein with a proteolysis tag green beads is released. Source I created this work entirely by myself. Date Author User Czwieb Czwieb User talk Czwieb talk other versions Licensing PD self date March 2009 ... more details
Wiktionary hmm HMM may refer to Hammerton railway station , England, National Rail station code HMM Hidden Markov model , a statistical model Heroes of Might and Magic , a series of turn based strategy games by New World Computing List of active United States Marine Corps aircraft squadrons Marine Medium Helicopter Squadrons Marine Medium Helicopter Squadrons , United States Marine Corps squadrons that fly the CH 46 Sea Knight helicopter Homenmen , an Armenian sporting organization Hyundai Merchant Marine , a South Korean logistics company Heavy meromyosin , a fragment obtained from the muscle protein myosin II following limited proteolysis Heavy metal music , a subgenre of rock music Hum sound , a sound one makes when thinking, eg. Hmm, I wonder.. . Disambiguation ko HMM it HMM ja HMM ru HMM ... more details
An exopeptidase is an enzyme produced in the pancreas that catalyst catalyses the removal of an amino acid from the end of a polypeptide chain. Exopeptidase cleaves the end of a polypeptide chain. Aminopeptidase , an enzyme in the brush border of the small intestine, will cleave a single amino acid from the aminoterminal. Carboxypeptidase , which is a digestive enzyme present in pancreatic juice, will cleave a single amino acid from the carboxylic end of the peptide. See also The Proteolysis Map Endopeptidase Edman degradation Dansyl chloride Protease External links MeshName Exopeptidases hydrolase stub Proteases Category Enzymes Category EC 3.4 de Exopeptidasen el fa it Esopeptidasi nl Exopeptidase pl Egzopeptydazy ru zh ... more details
Protein metabolism denotes the various biochemistry biochemical processes responsible for the synthesis of protein synthesis proteins and amino acid synthesis amino acids , and the breakdown of proteins and other large molecules, too by protein catabolism catabolism . Protein synthesis Main article Protein biosynthesis . Protein biosynthesis relies on four processes amino acid synthesis RNA synthesis Transcription genetics transcription Translation genetics translation Protein anabolism is the process by which protein are formed from amino acids aka anabolic amino acid synthesis . Protein catabolism is the process by which proteins are broken down to their amino acids. This is also called proteolysis . Metabolism DEFAULTSORT Protein Metabolism Category Metabolism Metabolism stub cs Metabolismus b lkovin ... more details
Peptidyl glutamyl peptide hydrolyzing PGPH enzyme activity is a means of proteolysis that cleaves peptide bond s in protein s immediately after acid ic or branched chain amino acid s. One of the three catalysis catalytic Protein subunit subunit s of the proteasome has PGPH activity and is strongly inhibited by the proteasome inhibitor epoxomicin . ref name Meng Meng L, Mohan R, Kwok BHB, Elofsson M, Sin N, Crews CM. 1999 . Epoxomicin, a potent and selective proteasome inhibitor, exhibits in vivo antiinflammatory activity. Proc Natl Acad Sci USA 96 18 10403 10408. ref References references External links http db.yeastgenome.org cgi bin GO go.pl?goid 45024 Gene Ontology entry hydrolase stub Category Posttranslational modification Category Metabolism Category EC 3.4 ... more details
Lactoferricin is an amphipathic , cationic peptide with anti microbial ref Wakabayashi H, Takase M, Tomita M. http www.ingentaconnect.com content ben cpd 2003 00000009 00000016 art00005 Lactoferricin derived from milk protein lactoferrin. Curr Pharm Des. 2003 9 16 1277 87. ref and anti cancer ref Eliassen LT, Berge G, Sveinbjornsson B, Svendsen JS, Vorland LH, Rekdal O. http cat.inist.fr ?aModele afficheN&cpsidt 14397614 Evidence for a direct antitumor mechanism of action of Bovine lactoferricin . Anticancer Res. 2002 Sep Oct 22 5 2703 10. ref properties. It can be generated by the pepsin mediated Proteolysis digestion of lactoferrin . References references biochem stub Category Biomolecules Category Peptides Lactoferricin ... more details
Multiple issues orphan February 2009 expert September 2009 context August 2009 unreferenced August 2009 Meromyosin mero meaning part of are subunits of the actin associated motor protein, myosin formed by trypsin digestion proteolysis . Following digestion, two types of meromyosin are formed heavy meromyosin HMM and light meromyosin LMM . Light meromyosin has a long, straight portion in the tail region. Heavy meromyosin is a protein chain terminating in a globular head portion cross bridge. HMM consists of two subunits, Heavy Meromyosin Subunit 1 and 2 HMMS 1 and HMMS 2 . The majority of myosin activity is concentrated in HMMS 1. HMMS 1 has an Actin binding site and Adenosine triphosphate ATP binding site myosin ATPase that determines the rate of muscle contraction when muscle is stretched. Category Motor proteins biochemistry stub ... more details
this page is a redirect basically to reversible or irreversible Post translational regulation refers to the Regulation of gene expression control of the levels of active protein. There are several forms. ref name Schumannnat. 2006 cite book author1 Wolfgang Schumann author2 Wolfgang Schumann Prof. Dr. rer. nat. title Dynamics of the bacterial chromosome structure and function url http books.google.com books?id pG7RgDra9lQC&pg PA266 accessdate 26 December 2010 year 2006 publisher Wiley VCH isbn 9783527304967 pages 266 ref It is performed either by means of reversible events Post translational modifications , such as Phosphorylation or sequestration or by means of irreversible events proteolysis . References reflist MolBioGeneExp Molecular Biology Category Gene expression Category Posttranslational modification fr R gulation post traductionnelle ... more details
Semenogelin is a protein that is involved in the formation of a gel matrix that encases ejaculated spermatozoa, preventing capacitation . ref name de Lamirande Cite journal author de Lamirande E, Lamothe G title Levels of semenogelin in human spermatozoa decrease during capacitation involvement of reactive oxygen species and zinc journal Hum Reprod volume issue pages year 2010 month May pmid 20501468 doi 10.1093 humrep deq110 url ref It blocks capacitation mainly via inhibition of reactive oxygen species ROS generation. ref name de Lamirande Proteolysis by prostate specific antigen PSA breaks down the gel matrix and allows the spermatozoa to move more freely. ref http www.ncbi.nlm.nih.gov sites entrez?Db gene&Cmd ShowDetailView&TermToSearch 6407 Entrez Gene SEMG2 semenogelin II ref There are two variants of the semenogelin protein Semenogelin 1 and Semenogelin 2 . References Reflist Biochemistry stub Category Proteins ... more details
A degron is a specific sequence of amino acids in a protein that directs the starting place of degradation. A degron sequence can occur at either the N or C terminal region, these are called N Degrons or C degrons respectively. A temperature sensitive degron takes advantage of the N end rule pathway, in which a destabilizing N terminal residue dramatically decreases the in vivo half life of a protein ref Dohmen, R.J., P. Wu, and A. Varshavsky, Heat inducible degron a method for constructing temperature sensitive mutants. Science, 1994. 263 5151 p. 1273 1276. ref . The degron is a fusion protein of ubiquitin , arginine , and DHFR . DHFR is dihydrofolate reductase, a mouse derived enzyme that functions in the synthesis of thymine. It is also heat labile at a higher temperature of 37 , becomes slightly unfolded and exposes an internal lysine , the site of multi ubiquitination. Proteolysis is highly processive, and the protein is degraded by the proteosome . The degron can be fused to a gene to produce the corresponding temperature sensitive protein. It is portable, and can be transferred on a plasmid. blockquote A ligand controllable degron takes advantage of a mutant form of FKBP12 protein that can be controlled using a synthetic ligand ref Schoeber JP, van de Graaf SF, Lee KP, Wittgen HG, Hoenderop JG, Bindels RJ,Conditional fast expression and function of multimeric TRPV5 channels using Shield 1.Am J Physiol Renal Physiol. 2009 Jan 296 1 F204 11 ref . Small molecule Shield1 binds specifically to the degron making it inactive. An inactive degron no longer promotes protein degradation. The degron is reactivated when the small molecule is removed by washing the cells and active protein degradation occurs through proteasome mediated proteolysis ref Chu BW, Banaszynski LA, Chen LC, Wandless TJ,Recent progress with FKBP derived destabilizing domains,Bioorg Med Chem Lett. 2008 Nov 15 18 22 5941 4 ref . blockquote References references See also N end rule Category Amino aci ... more details
Infobox Cheese name Fynbo image othernames country Denmark region town source cow pasteurised yes texture semi hard fat 34 protein dimensions weight 2 kg aging certification Fynbo is a semi hard Denmark Danish cheese named after the island of Fyn . It has a flavor of buckwheat and is processed with a combination of mesophile mesophilic and thermophile thermophilic bacterial cultures. Experiments with secondary proteolysis of Fynbo have helped to identify an important peptide produced during cheese ripening, s1 casein f1 23 ref cite journal author Sihufe GA, Zorrilla SE, Rubiolo AC title Secondary proteolysis of Fynbo cheese salted with NaCl KCl brine and ripened at various temperatures journal Food Chemistry volume 96 issue 2 pages 297 303 year 2006 doi 10.1016 j.foodchem.2005.02.026 url http www.sciencedirect.com science? ob ArticleURL& udi B6T6R 4FW7R26 4& user 10& rdoc 1& fmt & orig search& sort d& docanchor &view c& searchStrId 1141689606& rerunOrigin google& acct C000050221& version 1& urlVersion 0& userid 10&md5 4d2d732f93a865373c69bc93985116dc ref . This cheese was mentioned in Monty Python s Cheese Shop sketch . References Reflist External links http www.epicurious.com tools fooddictionary entry?id 5043 Epicurious Food Dictionary Tybo cheese Danish cheeses Cheese stub Category Danish cheeses Category Cow s milk cheeses pl Fynbo ... more details
The Signal Peptide Peptidase SPP and its homology chemistry homologs SPPL2a b c, SPPL3 are a class of transmembrane aspartyl protease s with the conserved motives YD ... GxGD ...PALL. Their sequences are highly conserved in different vertebrate species. Their substrates are Type II transmembrane proteins. ref cite journal author Weihofen A, Binns K, Lemberg MK, Ashman K, Martoglio B title Identification of signal peptide peptidase, a presenilin type aspartic protease journal Science volume 296 issue 5576 pages 2215 8 year 2002 pmid 12077416 doi 10.1126 science.1070925 ref Physiologically SPP processes signal peptides of HLA preproteins. A 9 AS cleavage fragment is then presented on HLA E receptors and modulates the activity of natural killer cells. ref cite journal author Lemberg MK, Bland FA, Weihofen A, Braud VM, Martoglio B title Intramembrane proteolysis of signal peptides an essential step in the generation of HLA E epitopes journal J. Immunol. volume 167 issue 11 pages 6441 6 year 2001 pmid 11714810 doi ref SPP also plays a pathophysiolocigal role it cleaves the core protein of Hepatitis C virus and thus influences the reproduction rate of HCV. ref cite journal author Okamoto K, Moriishi K, Miyamura T, Matsuura Y title Intramembrane proteolysis and endoplasmic reticulum retention of hepatitis C virus core protein journal J. Virol. volume 78 issue 12 pages 6370 80 year 2004 pmid 15163730 doi 10.1128 JVI.78.12.6370 6380.2004 pmc 416534 ref SPPL2a b promotes the intramembrane cleavage of TNF in activated dendritic cells and might play an immunomodulator y role. ref cite journal author Friedmann E, Hauben E, Maylandt K, et al. title SPPL2a and SPPL2b promote intramembrane proteolysis of TNFalpha in activated dendritic cells to trigger IL 12 production journal Nat. Cell Biol. volume 8 issue 8 pages 843 8 year 2006 pmid 16829952 doi 10.1038 ncb1440 ref ref cite journal author Fluhrer R, Grammer G, Israel L, et al. title A gamma secretase like intramembrane cleavage ... more details
Image Immunglobulin A as Dimer.png thumb right 180 px The protein dimer dimer ic IgA molecule. br 1 Immunoglobulin heavy chain H chain . br 2 Immunoglobulin light chain L chain . br 3 J chain . br 4 secretory component . The secretory component is a component of immunoglobulin A IgA which consists of a portion of the polymeric immunoglobulin receptor . Polymeric IgA binds to the polymeric immunoglobulin receptor on the basolateral surface of epithelial cells and is taken up into the cell via transcytosis . The receptor IgA complex passes through the cellular compartments before being secreted on the lumen anatomy luminal surface of the epithelial cells, still attached to the receptor. Proteolysis of the receptor occurs and the dimeric IgA molecule, along with the secretory component, are free to diffuse throughout the lumen. ref Cite journal author CS Kaetzel, JK Robinson, KR Chintalacharuvu, JP Vaerman, and ME Lamm title The polymeric immunoglobulin receptor secretory component mediates transport of immune complexes across epithelial cells a local defense function for IgA. journal Proc Natl Acad Sci USA volume 88 issue 19 pages 8796 8800 year 1991 pmid 1924341 doi 10.1073 pnas.88.19.8796 pmc 52597 ref External links MeshName Secretory component References Reflist Category Antibodies Immunology stub pl Fragment wydzielniczy ... more details
Other uses Mowse disambiguation Mowse MOWSE for MOlecular Weight SEarch is a method for identification of protein s from the molecular weight of peptide s created by Proteolysis proteolytic digestion and measured with mass spectrometry . ref name pmid15335725 cite journal author Pappin DJ, Hojrup P, Bleasby AJ title Rapid identification of proteins by peptide mass fingerprinting journal Curr. Biol. volume 3 issue 6 pages 327 32 year 1993 month June pmid 15335725 doi 10.1016 0960 9822 93 90195 T url http linkinghub.elsevier.com retrieve pii 0960 9822 93 90195 T ref The MOWSE algorithm was developed by Darryl Pappin and David Perkins at the Imperial Cancer Research Fund , and licensed from Cancer Research Technology. The probability based MOWSE score formed the basis of development of mascot software Mascot , a proprietary software for protein identification from mass spectrometry data. See also Peptide mass fingerprinting Mascot software References Reflist Bioinformatics stub Category Bioinformatics Category Mass spectrometry software Category Proteomics ... more details
limited proteolysis , depending on the amino acid sequence of a protein, or break down a complete peptide to amino acids unlimited proteolysis . The activity can be a destructive change, abolishing a protein ... of protease researchers, see the http www.protease.org International Proteolysis Society web page. See also The Proteolysis Map David Ho scientist David Ho , an AIDS researcher famous for pioneering ... International Proteolysis Society http merops.sanger.ac.uk Merops the peptidase database http www.sciencegateway.org ... MeshName Proteases http www.proteolysis.org Proteolysis MAP from Center for Proteolytic Pathways http cutdb.burnham.org Proteolysis Cut Site database curated expert annotation from users http substrate.burnham.org ... more details
Repressor LexA or LexA is a repressor enzyme EC number 3.4.21.88 that represses SOS response gene s coding for DNA polymerase s required for repairing DNA damage. LexA is intimately linked to RecA in the biochemical cycle of DNA damage and repair. RecA binds to DNA bound LexA causing LexA to cleave itself in a process called proteolysis autoproteolysis . DNA damage can be inflicted by the action of antibiotics. Bacteria require topoisomerase s such as DNA gyrase or topoisomerase IV for DNA replication . Antibiotics such as ciprofloxacin are able to prevent the action of these molecules by attaching themselves to the gyrase DNA complex. This is counteracted by the polymerase repair molecules from the SOS response . Unfortunately the action is partly counterproductive because ciprofloxacin is also involved in the synthetic pathway to RecA type molecules which means that the bacteria responds to an antibiotic by starting to produce more repair proteins. These repair proteins can lead to eventual benevolent mutations which can render the bacteria resistant to ciprofloxacin. Mutations are traditionally thought of as happening as a random process and as a liability to the organism. Many strategies exist in a cell to curb the rate of mutations. Mutations on the other hand can also be part of a survival strategy. For the bacteria under attack from an antibiotic, mutations help to develop the right biochemistry needed for defense. Certain polymerases in the SOS pathway are error prone in their copying of DNA which leads to mutations. While these mutations are often lethal to the cell, they can also lead to mutations which improve the bacteria s survival. In the specific case of topoisomerases, some bacteria have mutated one of their amino acids so that the ciproflaxin can only create a weak bond to the topoisomerase. This is one of the methods that bacteria use to become Antibiotic resistance resistant to antibiotics. Impaired LexA proteolysis has been shown to interfere wit ... more details
Refimprove date December 2009 Peptoids , or poly N substituted glycines, are a class of peptidomimetic s whose side chains are appended to the nitrogen atom of the peptide backbone, rather than to the carbons as they are in amino acid s . Chemical structure and synthesis File Peptoid struc synth.png frame text top Structure top and synthesis bottom of peptoids highlighting the submonomer approach. In peptoids the side chain is connected to the nitrogen of the peptide backbone, instead of the carbon as in peptides. Notably, peptoids lack the amide hydrogen which is responsible for many of the Secondary structure elements in peptides and proteins. Following the sub monomer protocol originally created by Ron Zuckermann, ref Efficient method for the preparation of peptoids oligo N substituted glycines by submonomer solid phase synthesis Journal of the American Chemical Society , 114 26 , 10646 10647, Ronald N. Zuckermann, Janice M. Kerr, Stephen B. H. Kent, Walter H. Moos DOI 10.1021 ja00052a076 ref each residue is installed in two steps acylation and displacement. In the acylation step a haloacetic acid, typically bromoacetic acid activated by diisopropylcarbodiimide reacts with the amine of the previous residue. In the displacement step a classical SN2 reaction S sub N sub 2 reaction , an amine displaces the halide to form the N substituted glycine residue. The submonomer approach allows the use of any commercially available or synthetically accessible amine with great potential for Combinatorial chemistry . Unique characteristics Like D Peptides and Beta peptide peptides peptoids are completely resistant to proteolysis , and are therefore advantageous for therapeutic applications where proteolysis is a major issue. Since secondary structure in peptoids does not involve hydrogen bonding, it is not typically Denaturation biochemistry denatured by solvent, temperature, or chemical denaturants such as urea . Notably, since the amino portion of the amino acid result ... more details
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