CYTOPLASMIC MEMBRANE LIPOPROTEIN LPPC OF STREPTOCOCCUS-EQUISIMILIS FUNCTIONS AS AN ACID-PHOSPHATASE

The function of the streptococcal cytoplasmic membrane lipoprotein, Lp pC,,vas identified with isogenic Streptococcus equisimilis H46A and Es cherichia coli JM109 strain pairs differing in whether they contained [H46A and JM109(pLPP2)] or lacked (H46A lppC::pLPP10 and JM109) the fu nctional lppC gene for comparative phosphatase determinations underaci dic conditions, lppC-directed acid phosphatase activity was demonstrat ed zymographically and by specific enzymatic activity assays, with who le cells or cell membrane preparations as enzyme sources, LppC acid ph osphatase showed optimum activity at pH 5, and the enzyme activity was unaffected by Triton X-100, L-(+)-tartaric acid, or EDTA, Database se arches revealed significant structural homology of LppC to the Strepto coccus pyogenes LppA, Flavobacterium meningosepticum OplA, Helicobacte r pylori HP1285, and Haemophilus influenzae Hel [e (P4)] proteins, The se results suggest a possible function for these proteins and establis h a novel function of streptococcal cell membrane lipoproteins.