1mc3

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Template:STRUCTURE 1mc3

CRYSTAL STRUCTURE OF RFFH

Overview

The enzyme glucose-1-phosphate thymidylyltransferase (RffH), the product of the rffh gene, catalyzes one of the steps in the synthesis of enterobacterial common antigen (ECA), a cell surface glycolipid found in Gram-negative enteric bacteria. In Escherichia coli two gene products, RffH and RmlA, catalyze the same enzymatic reaction and are homologous in sequence; however, they are part of different operons and function in different pathways. We report the crystal structure of RffH bound to deoxythymidine triphosphate (dTTP), the phosphate donor, and Mg(2+), refined at 2.6 A to an R-factor of 22.3% (R(free) = 28.4%). The crystal structure of RffH shows a tetrameric enzyme best described as a dimer of dimers. Each monomer has an overall alpha/beta fold and consists of two domains, a larger nucleotide binding domain (residues 1-115, 222-291) and a smaller sugar-binding domain (116-221), with the active site located at the domain interface. The Mg(2+) ion is coordinated by two conserved aspartates and the alpha-phosphate of deoxythymidine triphosphate. Its location corresponds well to that in a structurally similar domain of N-acetylglucosamine-1-phosphate uridylyltransferase (GlmU). Analysis of the RffH, RmlA, and GlmU complexes with substrates and products provides an explanation for their different affinities for Mg(2+) and leads to a proposal for the dynamics along the reaction pathway.

About this Structure

1MC3 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Crystal structure of Escherichia coli glucose-1-phosphate thymidylyltransferase (RffH) complexed with dTTP and Mg2+., Sivaraman J, Sauve V, Matte A, Cygler M, J Biol Chem. 2002 Nov 15;277(46):44214-9. Epub 2002 Aug 8. PMID:12171937 Page seeded by OCA on Sat May 3 00:52:34 2008