A novel solenoid fold in the cell wall anchoring domain of the pneumococcal virulence factor LytA.

Choline binding proteins are virulence determinants present in several Gram-positive bacteria. Because anchorage of these proteins to the cell wall through their choline binding domain is essential for bacterial virulence, their release from the cell surface is considered a powerful target for a weapon against these pathogens. The first crystal structure of a choline binding domain, from the toxin-releasing enzyme pneumococcal major autolysin (LytA), reveals a novel solenoid fold consisting exclusively of beta-hairpins that stack to form a left-handed superhelix. This unique structure is maintained by choline molecules at the hydrophobic interface of consecutive hairpins and may be present in other choline binding proteins that share high homology to the repeated motif of the domain.