1b8f
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(New page: 200px<br /><applet load="1b8f" size="450" color="white" frame="true" align="right" spinBox="true" caption="1b8f, resolution 2.1Å" /> '''HISTIDINE AMMONIA-LYA...)
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Revision as of 09:19, 20 November 2007
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HISTIDINE AMMONIA-LYASE (HAL) FROM PSEUDOMONAS PUTIDA
Overview
Histidine ammonia-lyase (EC 4.3.1.3) catalyzes the nonoxidative, elimination of the alpha-amino group of histidine and is closely related, to the important plant enzyme phenylalanine ammonia-lyase. The crystal, structure of histidase from Pseudomonas putida was determined at 2.1 A, resolution revealing a homotetramer with D2 symmetry, the molecular center, of which is formed by 20 nearly parallel alpha-helices. The chain fold, but not the sequence, resembles those of fumarase C and related proteins., The structure shows that the reactive electrophile is a, 4-methylidene-imidazole-5-one, which is formed autocatalytically by, cyclization and dehydration of residues 142-144 with the sequence, Ala-Ser-Gly. With respect to the first dehydration step, this modification, resembles the chromophore of the green fluorescent protein. The active, center is clearly established by the modification and by mutations. The, observed geometry allowed us to model the bound substrate at a high, confidence level. A reaction mechanism is proposed.
About this Structure
1B8F is a Single protein structure of sequence from Pseudomonas putida with SO4 and GOL as ligands. Active as Histidine ammonia-lyase, with EC number 4.3.1.3 Full crystallographic information is available from OCA.
Reference
Crystal structure of histidine ammonia-lyase revealing a novel polypeptide modification as the catalytic electrophile., Schwede TF, Retey J, Schulz GE, Biochemistry. 1999 Apr 27;38(17):5355-61. PMID:10220322
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