Transcription of Rhodospirillum rubrum atp operon

The photosynthetic non-sulphur bacterium Rhodospirillum rubrum contains a cluster of five genes encoding the subunits of F1-ATPase [Falk, Hampe & Walker (1985) Biochem. J. 228, 391-407]. Transcription of these genes has been studied by two methods, transcriptional mapping with S1 nuclease and primer extension analysis. Thereby a 5'-end in RNA derived from this region has been demonstrated at a guanine residue 236 bases before the initiation codon of the gene for the delta-subunit, the first in this cluster. DNA sequences on the 5' side of this nucleotide show some similarity to promoters in Escherichia coli, but are not apparently related to sequences upstream of the Rhodopseudomonas blastica atp operon. A 3'-end in RNA derived from this gene cluster has been demonstrated by S1-nuclease mapping. This is found before a run of thymidylate residues in the DNA, on the 3' side of a region of dyad symmetry. In E. coli these features are characteristic of rho-independent transcriptional termination signals. It appears from these studies and from the organization of the genes that the five genes in the atp cluster may be co-transcribed from this promoter and that transcripts terminate at the region of dyad symmetry.