Crystallization of a 67 kDa fragment of Escherichia coli DNA topoisomerase I.
Escherichia coli DNA topoisomerase I is a well-studied type I DNA topoisomerase that catalyzes the breakage and rejoining of one DNA strand to allow passage of the other strand. We have cloned and over-expressed a 67 kDa amino-terminal fragment of the protein, and shown that it retains the ability of the intact enzyme to cleave single-stranded DNA. High-quality crystals of the purified 67 kDa fragment have been obtained. The crystals belong to space group P2(1)2(1)2(1), with cell dimensions a = 64.0 A, b = 79.9 A and c = 142.3 A. They diffract to at least 2.8 A at low temperature and, when cooled to cryogenic temperatures, to at least 1.9 A in a synchrotron source. A complete native data set and two derivative data sets have been collected. A multiple isomorphous replacement map to 3 A resolution shows clear secondary structural elements. Final structure determination is in progress.
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208.
C D
CD
Lima
J C
JC
Wang
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A
Mondragón
D003460:Crystallization; D004264:DNA Topoisomerases, Type I / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D014961:X-Ray Diffraction
D010446:Peptide Fragments; D011994:Recombinant Proteins; D004264:DNA Topoisomerases, Type I