1f9a
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(New page: 200px<br /><applet load="1f9a" size="450" color="white" frame="true" align="right" spinBox="true" caption="1f9a, resolution 2.0Å" /> '''CRYSTAL STRUCTURE ANA...)
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Revision as of 12:36, 20 November 2007
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CRYSTAL STRUCTURE ANALYSIS OF NMN ADENYLYLTRANSFERASE FROM METHANOCOCCUS JANNASCHII
Overview
BACKGROUND: Nicotinamide adenine dinucleotide (NAD(+)) is an essential, cofactor involved in fundamental processes in cell metabolism. The enzyme, nicotinamide mononucleotide adenylyltransferase (NMN AT) plays a key role, in NAD(+) biosynthesis, catalysing the condensation of nicotinamide, mononucleotide and ATP, and yielding NAD(+) and pyrophosphate. Given its, vital role in cell life, the enzyme represents a possible target for the, development of new antibacterial agents. RESULTS: The structure of NMN AT, from Methanococcus jannaschii in complex with ATP has been solved by X-ray, crystallography at 2.0 A resolution, using a combination of single, isomorphous replacement and density modification techniques. The structure, reveals a hexamer with 32 point group symmetry composed of alpha/beta, topology subunits. The catalytic site is located in a deep cleft on the, surface of each subunit, where one ATP molecule and one Mg(2+) are, observed. A strictly conserved HXGH motif (in single-letter amino acid, code) is involved in ATP binding and recognition. CONCLUSIONS: The, structure of NMN AT closely resembles that of phosphopantetheine, adenylyltransferase. Remarkably, in spite of the fact that the two enzymes, share the same fold and hexameric assembly, a striking difference in their, quaternary structure is observed. Moreover, on the basis of structural, similarity including the HXGH motif, we identify NMN AT as a novel member, of the newly proposed superfamily of nucleotidyltransferase alpha/beta, phosphodiesterases. Our structural data suggest that the catalytic, mechanism does not rely on the direct involvement of any protein residues, and is likely to be carried out through optimal positioning of substrates, and transition-state stabilisation, as is proposed for other members of, the nucleotidyltransferase alpha/beta phosphodiesterase superfamily.
About this Structure
1F9A is a Single protein structure of sequence from Methanocaldococcus jannaschii with MG and ATP as ligands. Full crystallographic information is available from OCA.
Reference
Structure of nicotinamide mononucleotide adenylyltransferase: a key enzyme in NAD(+) biosynthesis., D'Angelo I, Raffaelli N, Dabusti V, Lorenzi T, Magni G, Rizzi M, Structure. 2000 Sep 15;8(9):993-1004. PMID:10986466
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