Active-site gating regulates substrate selectivity in a chymotrypsin-like serine protease the structure of haemophilus influenzae immunoglobulin A1 protease.

ABSTRACT: We report here the first structure of a member of the immunoglobulin A protease (IgAP) family at 1.75-A resolution. This protease is a founding member of the type V (autotransporter) secretion system and is considered a virulence determinant among the bacteria expressing the enzyme. The structure of the enzyme fits that of a classic autotransporter in which several unique domains necessary for protein function are appended to a central, 100-A-long beta-helical domain. The N-terminal domain of the IgAP is found to possess a chymotrypsin-like fold. However, this catalytic domain contains a unique loop D that extends over the active site acting as a lid, gating substrate access. The data presented provide a structural basis for the known ability of IgAPs to cleave only the proline/serine/thre

SUBMITTER: Johnson TA 

PROVIDER: S-EPMC2720633 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature