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1o88
From Proteopedia
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PECTATE LYASE C FROM ERWINIA CHRYSANTHEMI AT PH 11.2 WITH 30MM CA2+
Overview
Ca(2+) is essential for in vitro activity of Erwinia chrysanthemi pectate, lyase C (PelC). Crystallographic analyses of 11 PelC-Ca(2+) complexes, formed at pH 4.5, 9.5, and 11.2 under varying Ca(2+) concentrations, have, been solved and refined at a resolution of 2.2 A. The Ca(2+) site, represents a new motif for Ca(2+), consisting primarily of beta-turns and, beta-strands. The principal differences between PelC and the PelC-Ca(2+), structures at all pH values are the side-chain conformations of Asp-129, and Glu-166 as well as the occupancies of four water molecules. According, to calculations of pK(a) values, the presence of Ca(2+) and associated, structural changes lower the pK(a) of Arg-218, the amino acid responsible, for proton abstraction during catalysis. The Ca(2+) affinity for PelC is, weak, as the K(d) was estimated to be 0.132 (+/-0.004) mm at pH 9.5, 1.09, (+/-0.29) mm at pH 11.2, and 5.84 (+/-0.41) mm at pH 4.5 from x-ray, diffraction studies and 0.133 (+/-0.045) mm at pH 9.5 from intrinsic, tryptophan fluorescence measurements. Given the pH dependence of Ca(2+), affinity, PelC activity at pH 4.5 has been reexamined. At saturating, Ca(2+) concentrations, PelC activity increases 10-fold at pH 4.5 but is, less than 1% of maximal activity at pH 9.5. Taken together, the studies, suggest that the primary Ca(2+) ion in PelC has multiple functions.
About this Structure
1O88 is a Single protein structure of sequence from Erwinia chrysanthemi with CA as ligand. Active as Pectate lyase, with EC number 4.2.2.2 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
Reference
Characterization and implications of Ca2+ binding to pectate lyase C., Herron SR, Scavetta RD, Garrett M, Legner M, Jurnak F, J Biol Chem. 2003 Apr 4;278(14):12271-7. Epub 2003 Jan 22. PMID:12540845
Page seeded by OCA on Mon Nov 5 16:46:18 2007
