1yrl
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(New page: 200px<br /><applet load="1yrl" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yrl, resolution 2.6Å" /> '''Escherichia coli keto...)
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Revision as of 04:53, 21 November 2007
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Escherichia coli ketol-acid reductoisomerase
Overview
Ketol-acid reductoisomerase (KARI; EC 1.1.1.86) catalyzes two steps in the, biosynthesis of branched-chain amino acids. Amino acid sequence, comparisons across species reveal that there are two types of this enzyme:, a short form (Class I) found in fungi and most bacteria, and a long form, (Class II) typical of plants. Crystal structures of each have been, reported previously. However, some bacteria such as Escherichia coli, possess a long form, where the amino acid sequence differs appreciably, from that found in plants. Here, we report the crystal structure of the E., coli enzyme at 2.6 A resolution, the first three-dimensional structure of, any bacterial Class II KARI. The enzyme consists of two domains, one with, mixed alpha/beta structure, which is similar to that found in other, pyridine nucleotide-dependent dehydrogenases. The second domain is mainly, alpha-helical and shows strong evidence of internal duplication., Comparison of the active sites between KARI of E. coli, Pseudomonas, aeruginosa, and spinach shows that most residues occupy conserved, positions in the active site. E. coli KARI was crystallized as a tetramer, the likely biologically active unit. This contrasts with P. aeruginosa, KARI, which forms a dodecamer, and spinach KARI, a dimer. In the E. coli, KARI tetramer, a novel subunit-to-subunit interacting surface is formed by, a symmetrical pair of bulbous protrusions.
About this Structure
1YRL is a Single protein structure of sequence from Escherichia coli with SO4 as ligand. Active as Ketol-acid reductoisomerase, with EC number 1.1.1.86 Full crystallographic information is available from OCA.
Reference
The crystal structure of a bacterial class II ketol-acid reductoisomerase: domain conservation and evolution., Tyagi R, Duquerroy S, Navaza J, Guddat LW, Duggleby RG, Protein Sci. 2005 Dec;14(12):3089-100. PMID:16322583
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