Teichoic acids (cf. Greek τεῖχος, teīkhos, "wall", to be specific a fortification wall, as opposed to τοῖχος, toīkhos, a regular wall) are bacterial polysaccharides of glycerol phosphate or ribitol phosphate linked via phosphodiester bonds.
Location and structure
Teichoic acids are found within the cell wall of Gram-positive bacteria such as species in the genera Staphylococcus, Streptococcus, Bacillus, Clostridium, Corynebacterium, and Listeria, and appear to extend to the surface of the peptidoglycan layer. Teichoic acids are not found in Gram-negative bacteria. They can be covalently linked to <i>N-acetylmuramic acid of the peptidoglycan layer, to the lipids of the cytoplasmic membrane, or to a terminal D-alanine in the tetrapeptide crosslinkage between N-acetylmuramic acid units. Teichoic acids that remain anchored to lipids are referred to as lipoteichoic acids, whereas teichoic acids that are covalently bound to peptidoglycan are referred to as wall teichoic acids.
Function
The main function of teichoic acids is to provide rigidity to the cell-wall by attracting cations such as magnesium and sodium. Teichoic acids are usually, but not always, substituted with D-alanine ester residues, giving the molecule zwitterionic properties. These zwitterionic teichoic acids are suspected ligands for toll-like receptors 2 and 4. Teichoic acids also assist in regulation of cell growth by limiting the ability of autolysins to break the β(1-4) bond between the N-acetyl glucosamine and the N-acetylmuramic acid.
Lipoteichoic acids also act as receptor molecules for some Gram-positive bacteriophage. Evidence suggests teichoic acid may act as a bacteriophage receptor; however, this has not yet been conclusively supported.
See also
- Lipoteichoic acid - a major constituent of the cell wall of gram-positive bacteria
- Sir James Baddiley
0 komentar :
Posting Komentar