Biological Properties Of Cvh Gene Cluster And Hmr19 Gene From Streptomyces Hygroscopicus 10-22

FramePlot2.3.2 software analysis result showed that there were 29 open reading frames (ORF) on the 36.7 kb insertion fragment in a genomic library plasmid pHZ1392 of Streptomyces hygroscopicus 10-22. Among them a gene cluster consisting of five open reading frames was identified and designated cvh (cvn homolog of S. hygroscopicus 10-22) due to being highly homologous to the four-gene cvn11 cluster with its immediate downstream gene predicted to encode cytochrome P450 (SCO0588-84) in Streptomyces coelicolor A3(2), the genes of the cvh cluster were designated cvhA, B, C, D and E. The cvh-like clusters are commonly present in streptomycetes, there are 13 and 11 homologs in the completed genome of Streptomyces coelicolor A3(2) and Streptomyces avermitilis MA4680, respectively. Besides cvh gene cluster, a multi-drug efflux protein-encoding gene was also identified in the 36.7 kb genomic fragment and designated hmr19. In this study, we focused on the biological properties of cvh gene cluster and hmr19 gene, the results are as follows.(1) As the first gene of cvh cluster, cvhA encoded a putative sensor histidine kinase with a predicted sensor domain consisting of two trans-membrane segments at the N-terminus and a conserved HATPase_c domain at the C-terminus. The C-terminus polypeptide of CvhA expressed in Escherichia coli was purified and shown to be autophosphorylated with [γ-32P]ATP in vitro. The phosphoryl group was acid-labile and basic-stable, which supported histidine as the phosphorylation residue.