Abstract
A transcriptional regulation of the Pst system, an ABC Phosphate Transport System, of the Denitrifying Phototroph Rhodobacter sphaeroides f. sp. denitrificans was studied. The Pst system consisted of six genes similar to pstSCAB and phoUB, and its upstream sequence contained a putative regulatory sequence that is analogous to the Pho box involved in phosphate-limitation-induced gene expression in Escherichia coli. Both the amount of the PstS protein and the pstS promoter-driven expression of lacZ activity increased about 2-fold in response to phosphate limitation. Northern blot analysis of the Pst locus showed two different bands, which corresponded to pstS and pstCAB mRNA, suggesting that pstS and pstCAB transcribed by different promoters. The upstream sequence of pstC and phoU had no apparent Pho box, suggesting that the transcriptional regulation of pstCAB and phoUB is not regulated by pho regulon.
