2r0t
From Proteopedia
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Crystal sructure of GDP-4-keto-6-deoxymannose-3-dehydratase with a trapped PLP-glutamate geminal diamine
Overview
Di- and trideoxysugars are an important class of carbohydrates synthesized, by certain plants, fungi, and bacteria. Colitose, for example, is a, 3,6-dideoxysugar found in the O-antigens of Gram-negative bacteria such as, Escherichia coli, Salmonella enterica, Yersinia pseudotuberculosis, and, Vibrio cholerae, among others. These types of dideoxysugars are thought to, serve as antigenic determinants and to play key roles in bacterial defense, and survival. Four enzymes are required for the biochemical synthesis of, colitose starting from mannose-1-phosphate. The focus of this, investigation, GDP-4-keto-6-deoxy-d-mannose-3-dehydratase (ColD), catalyzes the third step in the pathway, namely the PLP-dependent removal, of the C3'-hydroxyl group from GDP-4-keto-6-deoxymannose. Whereas most, PLP-dependent enzymes contain an active site lysine, ColD utilizes a, histidine as its catalytic acid/base. The ping-pong mechanism of the, enzyme first involves the conversion of PLP to PMP followed by the, dehydration step. Here we present the three-dimensional structure of a, site-directed mutant form of ColD whereby the active site histidine has, been replaced with a lysine. The electron density reveals that the geminal, diamine, a tetrahedral intermediate in the formation of PMP from PLP, has, been trapped within the active site region. Functional assays further, demonstrate that this mutant form of ColD cannot catalyze the dehydration, reaction.
About this Structure
2R0T is a Single protein structure of sequence from Escherichia coli with as ligand. Full crystallographic information is available from OCA.
Reference
A Structural Study of GDP-4-Keto-6-Deoxy-d-Mannose-3-Dehydratase: Caught in the Act of Geminal Diamine Formation(,)., Cook PD, Holden HM, Biochemistry. 2007 Dec 11;46(49):14215-24. Epub 2007 Nov 13. PMID:17997582
Page seeded by OCA on Wed Jan 23 11:35:04 2008
