ISSN:
1617-4623
Keywords:
Superoperon
;
Overlapping operons
;
Photosynthetic bacteria
;
Bacteriochlorophyll
;
Puf
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Three adjacent operons, each concerned with photosynthesis in Rhodobacter capsulatus, have been shown by genetic means to be cotranscribable. In the course of describing the characteristics of the bchCA operon, which encodes two enzymes essential for bacteriochlorophyll synthesis, we found that the expression of the bchCA genes is influenced by readthrough from the upstream crtE and crtF genes. The crtE and crtF genes encode enzymes required for carotenoid biosynthesis and function as an operon. Furthermore, the distal structural gene of the bchCA operon, bchA, contains within it both the major oxygen-regulated promotor (Ppuf1) and the constitutive (Ppuf2) promotor for the puf operon. Since these three operons, crtEF, bchCA, and puf, are all transcribed in the same direction, it appears that polymerases traversing the down-stream regions may start at any of several promoters. This pattern of transcription, which is unusual among bacteria, demonstrates that the activities of individual operons in a superoperonal cluster may be affected by their positions within the cluster.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00330558
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