1d6m
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(New page: 200px<br /><applet load="1d6m" size="450" color="white" frame="true" align="right" spinBox="true" caption="1d6m, resolution 3.00Å" /> '''CRYSTAL STRUCTURE OF...)
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Revision as of 10:55, 20 November 2007
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CRYSTAL STRUCTURE OF E. COLI DNA TOPOISOMERASE III
Overview
BACKGROUND: DNA topoisomerases are enzymes that change the topology of, DNA. Type IA topoisomerases transiently cleave one DNA strand in order to, pass another strand or strands through the break. In this manner, they can, relax negatively supercoiled DNA and catenate and decatenate DNA, molecules. Structural information on Escherichia coli DNA topoisomerase, III is important for understanding the mechanism of this type of enzyme, and for studying the mechanistic differences among different members of, the same subfamily. RESULTS: The structure of the intact and fully active, E. coli DNA topoisomerase III has been solved to 3.0 A resolution. The, structure shows the characteristic fold of the type IA topoisomerases that, is formed by four domains, creating a toroidal protein. There is, remarkable structural similarity to the 67 kDa N-terminal fragment of E., coli DNA topoisomerase I, although the relative arrangement of the four, domains is significantly different. A major difference is the presence of, a 17 amino acid insertion in topoisomerase III that protrudes from the, side of the central hole and could be involved in the catenation and, decatenation reactions. The active site is formed by highly conserved, amino acids, but the structural information and existing biochemical and, mutagenesis data are still insufficient to assign specific roles to most, of them. The presence of a groove in one side of the protein is suggestive, of a single-stranded DNA (ssDNA)-binding region. CONCLUSIONS: The, structure of E. coli DNA topoisomerase III resembles the structure of E., coli DNA topoisomerase I except for the presence of a positively charged, loop that may be involved in catenation and decatenation. A groove on the, side of the protein leads to the active site and is likely to be involved, in DNA binding. The structure helps to establish the overall mechanism for, the type IA subfamily of topoisomerases with greater confidence and, expands the structural basis for understanding these proteins.
About this Structure
1D6M is a Single protein structure of sequence from Escherichia coli. Active as DNA topoisomerase, with EC number 5.99.1.2 Full crystallographic information is available from OCA.
Reference
The structure of Escherichia coli DNA topoisomerase III., Mondragon A, DiGate R, Structure. 1999 Nov 15;7(11):1373-83. PMID:10574789
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