Molecular cloning and DNA sequence analysis of Escherichia coli topB, the gene encoding topoisomerase III.

摘要: Escherichia coli contains two type 1 topoisomerases, topoisomerase I and III. Although III can be purified as a potent decatenase, its role in DNA metabolism is unclear. In order to address this issue, the gene encoding from E. has been molecularly cloned sequence determined. The fragment of an open reading frame that encode polypeptide 73.2 kDa. first 20 amino acids are identical those determined by amino-terminal gas-phase microsequencing. Expression encoded frame, using bacteriophage T7 transient expression system, results accumulation 74-kDa polypeptide. Soluble extracts prepared cells overexpressing product show dramatic increase activity when compared with control extracts. We propose designated topB.