Diferenzas entre revisións de «Peptidoglicano»

sen resumo de edición
O peptidoglicano exerce un papel estrutural na célula bacteriana, dándolle forza estrutural, e protexéndoa da [[presión osmótica]] exercida polo [[citoplasma]]. Aínda que o peptidoglicanolle dá forza estrutural á parede, para a determinación da súa forma necesítanse tamén as proteínas [[MreB]] e [[RodZ]]. <ref name="pmid11544518">{{cite journal| author=van den Ent F, Amos LA, Löwe J| title=Prokaryotic origin of the actin cytoskeleton. | journal=Nature | year= 2001 | volume= 413 | issue= 6851 | pages= 39–44 | pmid=11544518 | doi=10.1038/35092500 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11544518 }} </ref><ref name="pmid20168300">{{cite journal| author=van den Ent F, Johnson CM, Persons L, de Boer P, Löwe J| title=Bacterial actin MreB assembles in complex with cell shape protein RodZ. | journal=EMBO J | year= 2010 | volume= 29 | issue= 6 | pages= 1081–90 | pmid=20168300 | doi=10.1038/emboj.2010.9 | pmc=2845281 }} </ref> O peptidoglicano está tamén implicado na [[fisión binaria]] durante a división celular bacteriana.
 
TheA peptidoglycancapa layerde ispeptidoglicano substantiallyé thickermoito inmáis grosa nas bacterias [[Gram-positivepositiva]]s, [[bacteria]]nas que ten entre (20 toe 80 nanometers)[[nanómetro]]s de grosor, thanca innas [[Gram-negativenegativa]]s, bacterianas que só ten entre (7 toe 8 nanometers)nanómetros, withcoa theadhesión attachment of thedunha [[capa S-layer]]. PeptidoglycanO formspeptidoglicano aroundconstitúe arredor do 90 % of thedo [[drypeso weightseco]] ofdas bacterias Gram-positivepositivas, bacteriapero but onlyo 10% ofdas Gram-negative strainsnegativas. ThusDeste modo, presencea ofpresenza highde levelsgrandes ofcantidades peptidoglycande ispeptidoglicano theé primarya determinantcaracterística ofprincipal thedas characterisationpara of bacteriacaracterizar as grambacterias Gram-positivepositivas. <ref>C.Michael Hogan. 2010. [http://www.eoearth.org/article/Bacteria?topic=49480 ''Bacteria''. Encyclopedia of Earth. eds. Sidney Draggan and C.J.Cleveland, National Council for Science and the Environment, Washington DC]</ref> Nas Inbacterias Gram-positivepositivas strains,o itpeptidoglicano isé importantimportante inpara attachmenta rolesadhesión anda stereotypingsuperficies purposese para o estereotipado. <ref name=Salton1996>{{citecita booklibro | authorautor = Salton MRJ, Kim KS | titletítulo = Structure. ''In:'' Baron's Medical Microbiology ''(Barron S ''et al.'', eds.)| editionedición = 4th | publishereditor = Univ of Texas Medical Branch | yearano = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.289#297 | isbn=0-9631172-1-1 }}</ref> ForAs bothpartículas Gram-positivede andaproximadamente Gram-negative2 bacteria,nanómetros particlespoden ofatravesar approximatelyo 2&nbsp;nmpeptidoglicano, cantanto passnas throughGram-positivas thecoma nas peptidoglycannegativas. <ref>{{cite journal | author=Demchick PH, Koch AL | title=The permeability of the wall fabric of Escherichia coli and Bacillus subtilis | journal=Journal of Bacteriology | date=1 February 1996| pages=768–73| volume=178 | issue=3 |url=http://jb.asm.org/cgi/reprint/178/3/768 | pmid=8550511 | pmc=177723 }}</ref>
 
== Estrutura ==
[[ImageFicheiro:Peptidoglycan en.svg|thumb|PeptidoglycanPeptidoglicano.]]
The peptidoglycan layer in the bacterial cell wall is a [[crystal lattice]] structure formed from linear chains of two alternating amino [[sugar]]s, namely [[N-Acetylglucosamine|''N''-acetylglucosamine]] (GlcNAc or NAG) and [[N-Acetylmuramic acid|''N''-acetylmuramic acid]] (MurNAc or NAM). The alternating sugars are connected by a β-(1,4)-[[glycosidic bond]]. Each MurNAc is attached to a short (4- to 5-residue) [[amino acid]] chain, containing [[alanine|<small>L</small>-alanine]], [[glutamic acid|<small>D</small>-glutamic acid]], [[meso-diaminopimelic acid|''meso''-diaminopimelic acid]], and [[alanine|<small>D</small>-alanine]] in the case of ''[[Escherichia coli]]'' (a Gram-negative bacteria) or [[alanine|<small>L</small>-alanine]], [[glutamine|<small>D</small>-glutamine]], [[lysine|<small>L</small>-lysine]], and <small>D</small>-alanine with a 5-glycine interbridge between tetrapeptides in the case of ''[[Staphylococcus aureus]]'' (a Gram-positive bacteria). These amino acids, except the <small>L</small>-amino acids, do not occur in proteins and are thought to help protect against attacks by most peptidases{{Citation needed|date=November 2008}}.
 
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