1o8f: Difference between revisions
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==Overview== | ==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 ... | 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== | ==About this Structure== | ||
1O8F is a | 1O8F is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Erwinia_chrysanthemi Erwinia chrysanthemi] with CA as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Pectate_lyase Pectate lyase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.2.2 4.2.2.2] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1O8F OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: pectate lyase cleavage]] | [[Category: pectate lyase cleavage]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 14:00:39 2007'' | ||
