1k7g

From Proteopedia

---

Revision as of 16:48, 20 November 2007

proteopedia linkproteopedia link

spinqualitylabelsall models 1k7g, resolution 2.0Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

PrtC from Erwinia chrysanthemi

Overview

PrtC, a metallo-protease secreted by Erwinia chrysanthemi, is a member of, the serralysin family and hence belongs to the metzincin superfamily., While the crystal structures of representatives of all metzincin, subfamilies have been elucidated in the past, there is still some, controversy about the reaction mechanism and the role of certain, characteristic amino acids in the active centre. In this study, we probed, the role of Tyr228 and Glu189 by site-directed mutagenesis and X-ray, crystallography. There is evidence that these residues participate in, catalysis, although conflicting hypotheses have been proposed. The crystal, structures of wild-type and mutants have been refined to an R(free) of, about 0.20 at resolutions of 2.0 A or better. Exchange of Glu189 versus, alanine reduces the catalytic efficiency to less than 0.5 % using, resorufin casein as substrate and to about 3 % using an assay utilising, the thiol ester Ac-Pro-Leu-Gly-[(S)Leu]-Leu-Gly-OEt. The drop in activity, is caused by a reduction in k(cat) while the K(M) values are virtually the, same. In the resorufin casein assay, the mutant Y228F shows about 3 % of, the wild-type activity and in the thiol ester assay this increases to, about 56 %. In the latter case, the K(M) value of the mutant is increased, from 5.3 mM to 9.0 mM with only little reduction in k(cat). The different, behaviour of this mutant with respect to the two substrates can be, explained by a switch in the rate-determining step during catalysis. The, study presented here provides clear evidence that Glu189 of the, HEXXHXXGXXH motif is the catalytic base, while Tyr228 is more likely, involved in substrate binding and the stabilisation of the tetrahedral, transition state.

About this Structure

1K7G is a Single protein structure of sequence from Erwinia chrysanthemi with CA, ZN and PO4 as ligands. Full crystallographic information is available from OCA.

Reference

Protease C of Erwinia chrysanthemi: the crystal structure and role of amino acids Y228 and E189., Hege T, Baumann U, J Mol Biol. 2001 Nov 23;314(2):187-93. PMID:11718553

Page seeded by OCA on Tue Nov 20 18:55:16 2007