1O8J

Pectate Lyase C from Erwinia Chrysanthemi at pH 4.5 with 30mM CA2+

Summary for 1O8J

• Entry DOI: 10.2210/pdb1o8j/pdb
• Related: 1AIR 1O88 1O8D 1O8E 1O8F 1O8G 1O8H 1O8I 1O8K 1O8L 1O8M 1PLU 2PEC
• Descriptor: PECTATE LYASE C, CALCIUM ION (3 entities in total)
• Functional Keywords: hydrolase, pectate lyase cleavage, calcium binding, parallel beta-helix
• Biological source: ERWINIA CHRYSANTHEMI
• Total number of polymer chains: 1
• Total formula weight: 37773.68

Authors

Herron, S.R.,Jurnak, F.A. (deposition date: 2002-11-27, release date: 2003-01-30, Last modification date: 2023-12-13)

Primary citation

Herron, S.R.,Scavetta, R.,Garrett, M.,Legner, M.,Jurnak, F.A.
Characterization and Implications of Ca2+ Binding to Pectate Lyase C
J.Biol.Chem., 278:12271-12277, 2003

PubMed Abstract: 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.

PubMed: 12540845
DOI: 10.1074/JBC.M209306200

Experimental method

X-RAY DIFFRACTION (2.2 Å)