MOLECULAR ANALYSIS OF THE DNA GYRB GENE FROM MYXOCOCCUS-XANTHUS

DNA gyrase, an essential type II topoisomerase, mediates negative supe rcoiling of the bacterial chromosome, thereby affecting the processes of DNA replication, transcription, recombination and repair. The gyrB gene from the Gram-negative soil bacterium Myxococcus xanthus was sequ enced. The sequence predicts a protein of 815 amino acid residues disp laying significant homology to all known GyrB proteins. A 6-His-GyrB f usion protein was overexpressed in Escherichia coli and purified to ne ar homogeneity using affinity chromatography on Ni-nitrilotriacetic ac id-agarose and novobiocin-Sepharose columns. The fusion protein bound novobiocin and cross-reacted with anti-E. coli GyrB antibodies, indica ting structural and functional similarities to the E. coli DNA GyrB. T he gene was mapped to the region of the origin of replication (oriC) o f M. xanthus.