Pathways & interactions
Cell wall/choline-binding repeat (IPR018337)
Short name: Cell_wall/Cho-bd_repeat
The cell wall-binding repeat (CW) is an about 20 amino acid residue module, essentially found in two bacterial Gram-positive protein families; the choline binding proteins and glucosyltransferases (EC:126.96.36.199). In choline-binding proteins cell wall binding repeats bind to choline moieties of both teichoic and lipoteichoic acids, two components peculiar to the cell surface of Gram-positive bacteria [PMID: 2879828, PMID: 15539074]. In glucosyltransferases the region spanning the CW repeats is a glucan binding domain [PMID: 15576779].
Several crystal structures of CW have been solved [PMID: 11694890, PMID: 14527392]. In the choline binding protein LytA, the repeats adopt a solenoid fold consisting exclusively of beta-hairpins that stack to form a left-handed superhelix with a boomerang-like shape. The choline groups bind between beta-hairpin 'steps' of the superhelix [PMID: 11694890]. In Cpl-1 CW repeats assemble in two sub-domains: an N-terminal superhelical moiety similar to the LytA one and a C-terminal beta-sheet involved in interactions with the lysozyme domain. Choline is bound between repeats 1 and 2, and, 2 and 3 of the superhelical sub-domain [PMID: 14527392].Some proteins known to contain cell-wall binding repeats include:
- Pneumococcal N-acetylmuramoyl-L-alanine amidase (autolysin, lytA) (EC:188.8.131.52). It is a surface-exposed enzyme that rules the self-destruction of pneumococcal cells through degradation of their peptidoglycan backbone. It mediates the release of toxic substances that damage the host tissues.
- Pneumococcal endo-beta-N-acetylglucosaminidase (lytB) (EC:184.108.40.206). It plays an important role in cell wall degradation and cell separation.
- Pneumococcal teichoic acid phosphorylcholine esterase (pce or cbpE), a cell wall hydrolase important for cellular adhesion and colonisation.
- Lactobacillales glucosyltransferase. It catalyses the transfer of glucosyl units from the cleavage of sucrose to a growing chain of glucan.
- Clostridium difficile toxin A (tcdA) and toxin B (tcdb). They are the causative agents of the antibiotic-associated pseudomembranous colitis. They are intracellular acting toxins that reach their targets after receptor-mediated endocytosis.
- Clostridium acetobutylicum cspA protein.
- Siphoviridae bacteriophages N-acetylmuramoyl-L-alanine amidase. It lyses the bacterial host cell wall.
- Podoviridae lysozyme protein (cpl-1). It is capable of digesting the pneumococcal cell wall.
The cell wall binding repeats are also known as the choline-binding repeats (ChBr) or the choline-binding domain (ChBD).