The 1.7 Å crystal structure of the C5a peptidase from Streptococcus agalactiae (ScpB) reveals an active site competent for catalysis

Abstract

AbstractA 1.7 Å structure is presented for an active form of the virulence factor ScpB, the C5a peptidase from Streptococcus agalactiae. The previously reported structure of the ScpB active site mutant exhibited a large separation (~20 Å) between the catalytic His and Ser residues. Significant differences are observed in the catalytic domain between the current and mutant ScpB structures resulting with a high RMSDCα (4.6 Å). The fold of the active form of ScpB is nearly identical to ScpA (RMSDCα 0.2 Å), the C5a‐peptidase from Streptococcus pyogenes. Both ScpA and ScpB have comparable activity against human C5a, indicating neither enzyme require host proteins for C5a‐ase activity. These studies are a first step in resolving reported differences in the specificities of these enzymes.