title: Replacement of histidine 340 with alanine inactivates the group A Streptococcus extracellular cysteine protease virulence factor.
abstract: Streptococcus pyogenes expresses a highly conserved extracellular cysteine protease that is a virulence factor for invasive disease, including soft tissue infection. Site-directed mutagenesis was used to generate a His340Ala recombinant mutant protein that was made as a stable 40-kDa zymogen by Escherichia coli. Purified His340Ala protein was proteolytically inactive when bovine casein and human fibronectin were used as substrates. Wild-type 28-kDa streptococcal protease purified from S. pyogenes processed the 40-kDa mutant zymogen to a 28-kDa mature form, a result suggesting that the derivative protein retained structural integrity. The data are consistent with the hypothesis that His340 is an enzyme active site residue, an idea confirmed by recent solution of the zymogen crystal structure (T. F. Kagawa, J. C. Cooney, H. M. Baker, S. McSweeney, M. Liu, S. Gubba, J. M. Musser, and E. N. Baker, Proc. Natl. Acad. Sci. USA 97:2235-2240, 2000). The data provide additional insight into structure-function relationships in this S. pyogenes virulence factor.
authors.affiliation: Institute for the Study of Human Bacterial Pathogenesis, Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: S
authors.initials: S
authors.lastname: Gubba
authors.forename: V
authors.initials: V
authors.lastname: Cipriano
authors.forename: J M
authors.initials: JM
authors.lastname: Musser
mesh_terms: D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002364:Caseins / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics; D017124:Conserved Sequence; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006639:Histidine / Q000235:genetics; D008565:Membrane Proteins; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D002364:Caseins; D004792:Enzyme Precursors; D005098:Exotoxins; D005353:Fibronectins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C117980:SpeA protein, Streptococcus pyogenes; C027951:erythrogenic toxin; D006639:Histidine; D003546:Cysteine Endopeptidases; C042477:streptopain; D000409:Alanine