1irq
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(New page: 200px<br /><applet load="1irq" size="450" color="white" frame="true" align="right" spinBox="true" caption="1irq, resolution 1.50Å" /> '''Crystal structure of...)
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Revision as of 20:18, 24 November 2007
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Crystal structure of omega transcriptional repressor at 1.5A resolution
Overview
The 71 amino acid residue omega protein encoded by the Streptococcus, pyogenes non-conjugative plasmid pSM19035 is a transcriptional repressor, that regulates expression of genes for copy number control and stable, maintenance of plasmids. The crystal structure of omega protein has been, determined by multiple isomorphous replacement, including anomalous, scattering and refined to an R-factor of 21.1 % (R(free)=23.2 %) at 1.5 A, resolution. Two monomers related by a non-crystallographic 2-fold axis, form a homodimer that occupies the asymmetric unit. Each polypeptide chain, is folded into two alpha-helices and one beta-strand forming an, antiparallel beta-ribbon in the homodimer. The N-terminal regions (1-23, and 1-22 in subunits I and II, respectively) are not defined in the, electron density due to proteolysis of the N-terminal 20 amino acid, residues during crystallisation and partial disorder. The omega protein, belongs to the structural superfamily of MetJ/Arc repressors featuring a, ribbon-helix-helix DNA-binding motif with the beta-ribbon located in and, recognizing the major groove of operator DNA; according to a modelled, omega protein-DNA complex, residues Arg31 and Arg31' on the beta-ribbon, are in positions to interact with a nucleobase, especially guanine.
About this Structure
1IRQ is a Single protein structure of sequence from Streptococcus pyogenes. Full crystallographic information is available from OCA.
Reference
Crystal structure of omega transcriptional repressor encoded by Streptococcus pyogenes plasmid pSM19035 at 1.5 A resolution., Murayama K, Orth P, de la Hoz AB, Alonso JC, Saenger W, J Mol Biol. 2001 Dec 7;314(4):789-96. PMID:11733997
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