1ru4
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(New page: 200px<br /><applet load="1ru4" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ru4, resolution 1.60Å" /> '''Crystal structure of...)
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Revision as of 23:44, 20 November 2007
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Crystal structure of pectate lyase Pel9A
Overview
The "family 9 polysaccharide lyase" pectate lyase L (Pel9A) from Erwinia, chrysanthemi comprises a 10-coil parallel beta-helix domain with distinct, structural features including an asparagine ladder and aromatic stack at, novel positions within the superhelical structure. Pel9A has a single high, affinity calcium-binding site strikingly similar to the "primary", calcium-binding site described previously for the family Pel1A pectate, lyases, and there is strong evidence for a common second calcium ion that, binds between enzyme and substrate in the "Michaelis" complex. Although, the primary calcium ion binds substrate in subsite -1, it is the second, calcium ion, whose binding site is formed by the coming together of enzyme, and substrate, that facilitates abstraction of the C5 proton from the, sacharride in subsite +1. The role of the second calcium is to withdraw, electrons from the C6 carboxylate of the substrate, thereby acidifying the, C5 proton facilitating its abstraction and resulting in an E1cb-like, anti-beta-elimination mechanism. The active site geometries and mechanism, of Pel1A and Pel9A are closely similar, but the catalytic base is a lysine, in the Pel9A enzymes as opposed to an arginine in the Pel1A enzymes.
About this Structure
1RU4 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 Full crystallographic information is available from OCA.
Reference
The crystal structure of pectate lyase Pel9A from Erwinia chrysanthemi., Jenkins J, Shevchik VE, Hugouvieux-Cotte-Pattat N, Pickersgill RW, J Biol Chem. 2004 Mar 5;279(10):9139-45. Epub 2003 Dec 11. PMID:14670977
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