Cloning and characterization of the histidine biosynthetic gene cluster of Streptomyces coelicolor A3(2)

Biochemical and genetic data indicate that in Streptomyces coelicolor A3(2) the majority of the genes involved in the biosynthesis of histidine are clustered in a small region of the chromosome [Carere et al., Mol. Gen. Genet. 123 (1973) 219-224; Russi et al., Mol. Gen. Genet. 123 (1973) 225-232]. To investigate the structural organization and the regulation of these genes, we have constructed genomic libraries from S. coelicolor A3(2) in pUC vectors. Recombinant clones were isolated by complementation of an Escherichia coli hisBd auxotroph. A recombinant plasmid containing a 3.4-kb fragment of genomic DNA was further characterized. When cloned in the plasmid vector, pIJ699, this fragment was able to complement S. coelicolor A3(2) hisB mutants. Overlapping clones spanning a 15-kb genomic region were isolated by screening other libraries with labeled DNA fragments obtained from the first clone. Derivative clones were able to complement mutations in four different cistrons of the his cluster of S. coelicolor A3(2). Nucleotide sequence analysis of a 4-kb region allowed the identification of five ORFs which showed significant homology with the his gene products of E. coli. The order of the genes in S. coelicolor A3(2) (5'--hisD-hisC-hisBd-hisH-hisA-3') is the same as in the his operon of E. coli.