Unusual COOH-terminal structure of staphylococcal protease

The extracellular enzyme, staphylococcal protease, carries a COOH-terminal tryptic peptide of 43 amino acid residues most of which are aspartic acid, asparagine, and proline. This peptide might have a function equivalent to that of a similar segment previously observed at the NH2-terminal end of the membrane-bound penicillinase precursor of Bacillus licheniformis (Yamamoto, S., and Lampen, J. O. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 1457-1461). These observations would suggest that bacterial exoproteins which are secreted in the form of precursors differ from extracellular proteins by the presence of an extra segment at their NH2- and/or COOH-terminal ends.