title: Histidine and aspartic acid residues important for immunoglobulin G endopeptidase activity of the group A Streptococcus opsonophagocytosis-inhibiting Mac protein.
abstract: 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.
authors.affiliation: Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
authors.forename: Benfang
authors.initials: B
authors.lastname: Lei
authors.forename: Mengyao
authors.initials: M
authors.lastname: Liu
authors.forename: Elishia G
authors.initials: EG
authors.lastname: Meyers
authors.forename: Heather M
authors.initials: HM
authors.lastname: Manning
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Nagiec
authors.forename: James M
authors.initials: JM
authors.lastname: Musser
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D006639:Histidine; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009895:Opsonin Proteins / Q000502:physiology; D010587:Phagocytosis / Q000187:drug effects*; D013297:Streptococcus pyogenes / Q000737:chemistry / Q000276:immunology*; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D007074:Immunoglobulin G; D009895:Opsonin Proteins; D001224:Aspartic Acid; D006639:Histidine; D003546:Cysteine Endopeptidases