1o8h
From Proteopedia
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==Overview== | ==Overview== | ||
| - | Ca(2+) is essential for in vitro activity of Erwinia chrysanthemi pectate | + | 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== | ||
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[[Category: Pectate lyase]] | [[Category: Pectate lyase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Herron, S | + | [[Category: Herron, S R.]] |
| - | [[Category: Jurnak, F | + | [[Category: Jurnak, F A.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: calcium binding]] | [[Category: calcium binding]] | ||
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[[Category: pectate lyase cleavage]] | [[Category: pectate lyase cleavage]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:14:44 2008'' |
Revision as of 12:14, 21 February 2008
|
PECTATE LYASE C FROM ERWINIA CHRYSANTHEMI AT PH 9.5 WITH 0.3MM CA2+ ADDED
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
1O8H is a Single protein structure of sequence from Erwinia chrysanthemi with as ligand. Active as Pectate lyase, with EC number 4.2.2.2 Known structural/functional Site: . 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
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