Molecular analysis of three major wall-associated proteins of Bacillus subtilis 168: evidence for processing of the product of a gene encoding a 258 kDa precursor two-domain ligand-binding protein

Summary

Antisera raised to a 109 kDa wall-associated protein (WAP) of Bacillus subtilis 168 cross-reacts with two other WAPs of 220 and 58 kDa. The structural gene for the 109 kDa WAP (designated wapA) was cloned, sequenced, mapped at around 340° on the B. subtilis 168 chromosome and found to encode a precursor of all three wall-bound forms (2334 amino acids and 258 329 Da). The protein has two ligand-binding domains; the N-terminal domain has three direct repeats of 102 residues with 40% identity, which are responsible for wall binding. The C-terminal domain consists of two blocks of residues with a conserved motif repeated a total of 31 times. The motif consensus sequence GXXXX(Y,F)XYDXXG is almost identical to that of the Escherichia coli rearrangement hot spot family and shows similarity to a carbohydrate-binding motif of a number of Gram-positive secreted proteins. A mutant insertionally inactivated in the wapA gene had no distinguishable phenotype apart from lacking the three WAPs. The possible role of WAPA and its two-domain relationship with other ligand-binding proteins is discussed.