3h09 | pdb_00003h09

The structure of Haemophilus influenzae IgA1 protease

spinqualitylabelsall models 3h09, resolution 1.75Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3h09 is a 2 chain structure with sequence from Haemophilus influenzae. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: ACT, MLA, NA Activity: IgA-specific serine endopeptidase, with EC number 3.4.21.72 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum Function [IGA0_HAEIN] Virulence factor; cleaves host immunoglobulin A producing intact Fc and Fab fragments. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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/threonine-rich hinge peptide unique to IgA1 (isotype 1) in the context of the intact fold of the immunoglobulin. Based upon the structural data, as well as molecular modeling, a model suggesting that the unique extended loop D in this IgAP sterically occludes the active-site binding cleft in the absence of immunoglobulin binding is presented. Only in the context of binding of the IgA1-Fc domain in a valley formed between the N-terminal protease domain and another domain appended to the beta-helix spine (domain 2) is the lid stabilized in an open conformation. The stabilization of this open conformation through Fc association subsequently allows access of the hinge peptide to the active site, resulting in recognition and cleavage of the substrate. Active-site gating regulates substrate selectivity in a chymotrypsin-like serine protease the structure of haemophilus influenzae immunoglobulin A1 protease.,Johnson TA, Qiu J, Plaut AG, Holyoak T J Mol Biol. 2009 Jun 12;389(3):559-74. Epub 2009 Apr 23. PMID:19393662 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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