1jsz
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(New page: 200px<br /><applet load="1jsz" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jsz, resolution 1.93Å" /> '''Crystal Structure An...)
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Revision as of 16:25, 20 November 2007
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Crystal Structure Analysis of N7,9-dimethylguanine-VP39 complex
Overview
The N7-methylguanine portion of the mRNA cap structure interacts with, cap-binding proteins via an unusual double-stacking arrangement in which, the positively charged cap is sandwiched between two parallel-oriented, aromatic protein side chains. Three-dimensional costructures of cap with, two mRNA cap-binding proteins, namely, translational initiation factor, eIF4E and VP39 (the vaccinia virus-encoded mRNA cap-specific, 2'-O-methyltransferase), have heretofore been reported. Despite striking, similarities between the two proteins in the double stack with the cap, the stack differs most notably in the species of stacked side chain, donated by the protein. Whereas eIF4E employs two tryptophans, VP39 uses a, tyrosine and a phenylalanine. Here, we have generated tryptophan, substitutions in VP39. Tryptophan substitution was shown, crystallographically, not to disrupt the maintenance of a bona fide, parallel stack. However, the single-tryptophan and double-tryptophan, substitutions were associated with increased affinity for cap nucleoside, by factors of 10 and 50, respectively. VP39 interacted more strongly with, a true substrate (containing portions of RNA downstream of the cap in, addition to the cap itself) than with isolated cap nucleoside, by several, orders of magnitude. VP39 mutants with tryptophan substitution at position, 180 exhibited apparent defects in substrate catalytic rate during the, first turnover cycle, indicating the possibility of an exquisite, sensitivity of the catalytic center to subtle changes in substrate, position brought about by alterations in the cap-binding slot. The X-ray, structure of VP39 with a genuine nucleobase analogue of, N7-methylguanosine, namely, N7,9-dimethylguanine, indicated that the, N7-methylguanosine rotational orientation within the stack is a property, of the cap nucleobase itself.
About this Structure
1JSZ is a Single protein structure of sequence from Vaccinia virus with SAH and NDM as ligands. Active as Polynucleotide adenylyltransferase, with EC number 2.7.7.19 Full crystallographic information is available from OCA.
Reference
The "cap-binding slot" of an mRNA cap-binding protein: quantitative effects of aromatic side chain choice in the double-stacking sandwich with cap., Hu G, Oguro A, Li C, Gershon PD, Quiocho FA, Biochemistry. 2002 Jun 18;41(24):7677-87. PMID:12056899
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