Open AccessHistidine and Aspartic Acid Residues Important for Immunoglobulin G Endopeptidase Activity of the Group AStreptococcusOpsonophagocytosis-Inhibiting Mac Protein
Author(s) -
Benfang Lei,
Mengyao Liu,
Elishia G. Meyers,
Heather M. Manning,
Michael J. Nagiec,
James M. Musser
Publication year - 2003
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.71.5.2881-2884.2003
Subject(s) - endopeptidase , biology , biochemistry , aspartic acid , immunoglobulin g , microbiology and biotechnology , streptococcus pyogenes , enzyme , protein a , antibody , amino acid , bacteria , staphylococcus aureus , immunology , genetics
The secreted Mac protein made by serotype M1 group A Streptococcus (GAS) (designated Mac(5005)) inhibits opsonophagocytosis and killing of GAS by human polymorphonuclear neutrophils. This protein also has cysteine endopeptidase activity against human immunoglobulin G (IgG). Site-directed mutagenesis was used to identify histidine and aspartic acid residues important for Mac IgG endopeptidase activity. Replacement of His262 with Ala abolished Mac5005 IgG endopeptidase activity. Asp284Ala and Asp286Ala mutant proteins had compromised enzymatic activity, whereas 21 other Asp-to-Ala mutant proteins cleaved human IgG at the apparent wild-type level. The results suggest that His262 is an active-site residue and that Asp284 and Asp286 are important for the enzymatic activity or structure of Mac protein. These Mac mutants provide new information about structure-activity relationships in this protein and will assist study of the mechanism of inhibition of opsonophagocytosis and killing of GAS by Mac.