1b1a
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(New page: 200px<br /><applet load="1b1a" size="450" color="white" frame="true" align="right" spinBox="true" caption="1b1a" /> '''GLUTAMATE MUTASE (B12-BINDING SUBUNIT), NMR,...)
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Revision as of 09:09, 20 November 2007
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GLUTAMATE MUTASE (B12-BINDING SUBUNIT), NMR, MINIMIZED AVERAGE STRUCTURE
Overview
Glutamate mutase (Glm) is an adenosylcobamide-dependent enzyme that, catalyzes the reversible rearrangement of (2S)-glutamate to (2S, 3S)-3-methylaspartate. The active enzyme from Clostridium cochlearium, consists of two subunits (of 53.6 and 14.8 kDa) as an alpha2beta2, tetramer, whose assembly is mediated by coenzyme B12. The smaller of the, protein components, GlmS, has been suggested to be the B12-binding, subunit. Here we report the solution structure of GlmS, determined from a, heteronuclear NMR-study, and the analysis of important dynamical aspects, of this apoenzyme subunit. The global fold and dynamic behavior of GlmS in, solution are similar to those of the corresponding subunit MutS from C., tetanomorphum, which has previously been investigated using, NMR-spectroscopy. Both solution structures of the two Glm B12-binding, subunits share striking similarities with that determined by, crystallography for the B12-binding domain of methylmalonyl CoA mutase, (Mcm) from Propionibacterium shermanii, which is B12 bound. In the crystal, structure a conserved histidine residue was found to be coordinated to, cobalt, displacing the endogenous axial ligand of the cobamide. However, in GlmS and MutS the sequence motif, Asp-x-His-x-x-Gly, which includes the, cobalt-coordinating histidine residue, and a predicted alpha-helical, region following the motif, are present as an unstructured and highly, mobile loop. In the absence of coenzyme, the B12-binding site apparently, is only partially formed. By comparing the crystal structure of Mcm with, the solution structures of B12-free GlmS and MutS, a consistent picture on, the mechanism of B12 binding has been obtained. Important elements of the, binding site only become structured upon binding B12; these include the, cobalt-coordinating histidine residue, and an alpha helix that forms one, side of the cleft accommodating the nucleotide 'tail' of the coenzyme.
About this Structure
1B1A is a Single protein structure of sequence from Clostridium cochlearium. Active as Methylaspartate mutase, with EC number 5.4.99.1 Full crystallographic information is available from OCA.
Reference
Structure and dynamics of the B12-binding subunit of glutamate mutase from Clostridium cochlearium., Hoffmann B, Konrat R, Bothe H, Buckel W, Krautler B, Eur J Biochem. 1999 Jul;263(1):178-88. PMID:10429202
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