Genetic Polymorphisms of Group B StreptococcusscpBAlter Functional Activity of a Cell-Associated Peptidase That Inactivates C5a
- 1 September 2000
- journal article
- research article
- Published by American Society for Microbiology in Infection and Immunity
- Vol. 68 (9), 5018-5025
- https://doi.org/10.1128/iai.68.9.5018-5025.2000
Abstract
Many group BStreptococcus agalactiaestrains and other pathogenic streptococci express a cell-associated peptidase that inactivates C5a (C5a-ase), the major neutrophil chemoattractant produced by activation of the complement cascade. Type III group B streptococci (GBS) can be classified genotypically into three restriction digest pattern types. Functional C5a-ase activity of GBS correlates with this genetic typing; therefore, we sought to identify a genetic basis for this phenomenon. Southern hybridization confirms that all type III GBS containscpB, the gene encoding GBS C5a-ase. GBS strains with high C5a-ase functional activity and those with no or very low activity both express immunoreactive C5a-ase. ThescpBsequence of strain I30, which has high C5a-ase activity, is 98.2% homologous to the previously reported serotype II GBSscpBsequence. ThescpBsequences of strains I25 and GW, which have low or no C5a-ase activity, are identical. The predicted I25 and GW C5a-ase proteins share a four-amino-acid deletion affecting the protease histidine active-site consensus motif. Recombinant I30 C5a-ase has good functional activity, whereas recombinant I25 C5a-ase has low activity. These data demonstrate that functional C5a-ase differences between type III GBS strains are attributable to a genetic polymorphism ofscpB. The ubiquitous expression of C5a-ase, irrespective of functional activity, suggests that C5a-ase may have a second, as yet unidentified, function.Keywords
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