PMID:7510701
| Citation |
Zhang, HL and DiGate, RJ (1994) The carboxyl-terminal residues of Escherichia coli DNA topoisomerase III are involved in substrate binding. J. Biol. Chem. 269:9052-9 |
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| Abstract |
The nucleic acid-binding domain of Escherichia coli DNA topoisomerase III (Topo III) has been identified using a selection procedure designed to isolate inactive Topo III polypeptides. Deletion of this binding domain, contained in the carboxyl terminus of Topo III, results in a drastic reduction in the ability of the enzyme to bind to single-stranded DNA and RNA substrates. Successive truncation of the enzyme within this region results in the gradual loss of nucleic acid binding activity and in a gradual change in the mechanism of Topo III-catalyzed relaxation of negatively supercoiled DNA. The reduction of nucleic acid binding activity of the truncated polypeptides does not result in a loss of cleavage site specificity for the enzyme, suggesting that other amino acids are involved in the positioning of the nucleic acid within the nicking/closing site of the topoisomerase. |
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| Keywords |
Amino Acid Sequence; Base Sequence; Binding Sites; DNA Topoisomerases, Type I/chemistry; DNA Topoisomerases, Type I/metabolism; DNA, Single-Stranded/metabolism; DNA, Superhelical/metabolism; DNA-Binding Proteins/chemistry; DNA-Binding Proteins/metabolism; Escherichia coli/enzymology; Molecular Sequence Data; Oligodeoxyribonucleotides/chemistry; Protein Binding; RNA/metabolism; RNA-Binding Proteins/chemistry; RNA-Binding Proteins/metabolism; Structure-Activity Relationship |
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