Multi-domain, cell-envelope proteinases of lactic acid bacteria

The multi-domain, cell-envelope proteinases encoded by the genes prtB of La ctobacillus delbrueckii subsp. bulgaricus, prtH of Lactobacillus helveticus , prtP of Lactococcus lactis, scpA of Streptococcus pyogenes and csp of Str eptococcus agalactiae have been compared using multiple sequence alignment, secondary structure prediction and database homology searching methods. Th is comparative analysis has led to the prediction of a number of different domains in these cell-envelope proteinases, and their homology, characteris tics and putative function are described. These domains include, starting f rom the N-terminus, a pre-pro-domain for secretion and activation, a serine protease domain (with a smaller inserted domain), two large middle domains A and B of unknown but possibly regulatory function, a helical spacer doma in, a hydrophilic cell-wall spacer or attachment domain, and a cell-wall an chor domain. Not all domains are present in each cell-envelope proteinase, suggesting that these multi-domain proteins are the result of gene shufflin g and domain swapping during evolution.