S-layer


S-layer

An S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins. This two dimensional structure is built via self-assembly and encloses the whole cell surface. Thus, the S-layer protein can represent up to 10-15% of the whole protein content of a cellcite journal |author=Messner P, Sleytr U |title=Crystalline bacterial cell-surface layers |journal=Adv. Microb. Physiol. |volume=33 |issue= |pages=213–75 |year=1992 |pmid=1636510 |doi=10.1016/S0065-2911(08)60218-0] cite journal |author=Pum D, Messner P, Sleytr U |title=Role of the S layer in morphogenesis and cell division of the archaebacterium Methanocorpusculum sinense |journal=J. Bacteriol. |volume=173 |issue=21 |pages=6865–73 |year=1991 |pmid=1938891] cite journal |author=Sleytr U, Messner P, Pum D, Sára M |title=Crystalline bacterial cell surface layers |journal=Mol. Microbiol. |volume=10 |issue=5 |pages=911–6 |year=1993 |pmid=7934867 |doi=10.1111/j.1365-2958.1993.tb00962.x] . S-layer proteins are poorly or not conserved at all and can differ markedly even between related species.Depending on species the S-layers have a thickness between 5 and 25 nm and possess identical pores with 2-8 nm in diameter cite journal |author=Sleytr U, Bayley H, Sára M, Breitwieser A, Küpcü S, Mader C, Weigert S, Unger F, Messner P, Jahn-Schmid B, Schuster B, Pum D, Douglas K, Clark N, Moore J, Winningham T, Levy S, Frithsen I, Pankovc J, Beale P, Gillis H, Choutov D, Martin K |title=Applications of S-layers |journal=FEMS Microbiol. Rev. |volume=20 |issue=1-2 |pages=151–75 |year=1997 |pmid=9276930] . S-layers exhibit either an oblique (p1, p2), square (p4) or hexagonal (p3, p6) lattice symmetry. Depending on the lattice symmetry the S-layer is composed of one (P1), two (P2), three (P3), four (P4) or six (P6) identical protein subunits, respectively. The centre to centre spacings (or unit cell dimensions) between these subunits range between 2.5 and 35 nm.

Fixation of S-layers in the cell wall

* In Gram-negative bacteria S-layers are associated to the LPS via ionic, carbohydrate-carbohydrate, protein carbohydrate interactions and/or protein-protein interactions.
* In Gram-positive bacteria whose S-layers contain surface layer homology (SLH) domains the binding occurs to the peptidoglycan and to a secondary cell wall polymer (e.g. teichuronic acids). In the absence of SLH domains the binding occurs via electrostatic interactions between the positively charged N-terminus of the S-layer protein and a negatively charged secondary cell wall polymer.
*In Gram-negative archaea S-layer proteins possess a hydrophobic anchor that is associated with the underlying lipid membrane.
*In Gram-positive archaea the S-layer proteins bind pseudomurein or to methanochondritin.

Biological functions of the S-layer

As for many bacteria the S-layer represents the outermost interaction zone with their respective environment, its functions are very diverse and vary from species to species.In Archaea the S-layer is the only cell wall component and therefore is important for mechanical stabilisation. Additional functions associated with S-layers include:
* protection against bacteriophages and phagocytosis
* resistance against low pH
* barrier against high molecular weight substances (e.g. lytic enzymes)
* adhesion (for glycosylated S-layers)
* stabilisation of the membrane
* provide adhesion sites for exoproteins
* provide a periplasmic compartment in Gram-positive prokaryotes together with the peptidoglycan and the cytoplasmic membrane

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Layer Jump Recording (LJR) — is a writing method used for DVD R DL (Dual Layer).It permits recording the disc per increments called session (see Optical disc authoring), aka multi session. It also permits a faster closing of the disc by saving extraneous padding when the… …   Wikipedia

  • Layer 8 — is internet jargon which is used to refer to the user or political layer. [Citation last = Gregg first = Michael title = OSI: Securing the Stack, Layer 8 Social engineering and security policy journal = TechTarget date = 2007 05 01 year = 2007… …   Wikipedia

  • Layer — may refer to: * A layer of dieposits found on archaeological excavation isolated as a single context in the stratigraphy of the site * A layer hen, a hen raised to produce eggs. * In abstraction, a layer is an abstract place conceived as having… …   Wikipedia

  • layer — [ leje ] v. tr. <conjug. : 8> • 1307; probablt du frq. °lakan « munir d une marque indiquant une limite » ♦ Techn. 1 ♦ Faire traverser par un layon. Layer une forêt. Par ext. Délimiter (une superficie de bois) par une laie périphérique. 2 ♦ …   Encyclopédie Universelle

  • layer — lay‧er [ˈleɪə ǁ ər] noun [countable] HUMAN RESOURCES one of the levels in an organization: • We are operating with fewer layers of management. marzipan layer [ˈmɑːzpæn ˌleɪə ǁ ˈmɑːrtspæn ˌleɪər] [singular] …   Financial and business terms

  • Layer four traceroute — (LFT) is a fast traceroute engine, that also implements numerous other features including AS number lookups through several reliable sources, loose source routing, netblock name lookups, etc. and goes through many configurations of packet filter… …   Wikipedia

  • Layer — (engl. „Schicht, Lage“) steht für: dünne Schichten eines Werkstoffs im Mikrometer bis Nanometerbereich eine Schichtenarchitektur bei einem Softwaresystem ein Konzept für Kommunikationsprotokolle, 7 Layer Modell, siehe OSI Modell funktionale… …   Deutsch Wikipedia

  • Layer Cake — Données clés Réalisation Matthew Vaughn Scénario J.J. Connolly Acteurs principaux Daniel Craig Tom Hardy Jamie Foreman Sally Hawkins George Harris Sociétés de production …   Wikipédia en Français

  • Layer 3 — may refer to:* In computer network protocols, layer 3 refers to the network layer. * In neuroanatomy, layer 3 is one of the six layers of the cerebral cortex …   Wikipedia

  • Layer 2 Tunnelling Protocol — Layer 2 Tunneling Protocol Layer 2 Tunneling Protocol (L2TP) signifie protocole de tunnellisation de niveau 2. Il s agit d un protocole réseau utilisé pour créer des Virtual Private Networks (VPN), le plus souvent entre un opérateur de collecte… …   Wikipédia en Français

  • Layer 2 tunneling protocol — (L2TP) signifie protocole de tunnellisation de niveau 2. Il s agit d un protocole réseau utilisé pour créer des Virtual Private Networks (VPN), le plus souvent entre un opérateur de collecte de trafic (dégroupeur ADSL ou opérateur de téléphonie… …   Wikipédia en Français


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.