Expression and analysis of two gyrB genes from the novobiocin producer, Streptomyces sphaeroides.

A novobiocin producer, Streptomyces sphaeroides, contains two genes, designated gyrBS and gyrBR, that encode novobiocin-sensitive and -resistant DNA gyrase B proteins, respectively. The cloning of gyrBR was reported earlier; here, we describe the cloning of gyrBS. Both genes have been sequenced (the deduced products of gyrBS and gyrBR have M(r) values of 87.6K and 86.5K, respectively) and their transcripts have been mapped. Downstream of gyrBS, and co-transcribed with it, is the sole gyrA gene (encoding DNA gyrase A protein). By constructing hybrid gyrB genes, using fragments of gyrBS and gyrBR, a specific portion of the N-terminal domain of the gyrase B protein (corresponding to amino acid residues 134-256 of Escherichia coli gyrase B) has been implicated in the binding of novobiocin.