Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The crtEF, bchCA, and puf operons of the facultative phototrophic bacterium Rhodobacter capsulatus encode gene products that are necessary for the formation of various components of the photosynthetic apparatus. The crtEF operon encodes two enzymes involved in the biosynthesis of carotenoids, the bchCA operon codes for two enzymes of the bacteriochlorophyll biosynthetic pathway, and the puf operon encodes four pigment-binding polypeptides as well as two polypeptides with less well understood functions. These three operons are adjacent to one another on the chromosome and are transcribed in the same direction. We present the results of RNA blotting and S1 nuclease protection end-mapping experiments which provide direct evidence that the mRNA transcripts of these three operons overlap. Therefore, it is likely that the crtEF, bchCA, and puf operons can be expressed as a single transcriptional unit, although RNA polymerase may initiate transcription at any of several promoters.
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PMID:Overlapping mRNA transcripts of photosynthesis gene operons in Rhodobacter capsulatus. 199 90

Because there are not yet direct assays for most of the proteins required for differentiation of Rhodobacter capsulatus cytoplasmic membrane into photosynthetically competent intracytoplasmic membrane, a molecular inquiry into the mechanism and regulation of this process is difficult. We have, therefore, chosen to isolate R. capsulatus photosynthesis genes by creating in-frame fusions to lac'Z vectors, and selecting for those that direct appropriately regulated levels of beta-galactosidase in R. capsulatus. One lacZ fusion isolate was used to identify an open reading frame (ORF) of unknown function and flanking sequences that promoted initiation of transcription. The chromosomal copy of this ORF was mutated by insertion of a kanamycin-resistant cartridge into the cloned fragment and substitution for the chromosomal copy by homologous recombination. The phenotype of the resultant mutant cells showed that the ORF encodes 2-desacetyl-2-hydroxyethyl bacteriochlorophyllide a dehydrogenase, an enzyme that catalyzes the penultimate step in bacteriochlorophyll a biosynthesis. The nucleotide sequence of this bchC gene and its 5' regulatory region were determined. The deduced amino acid sequence shows that the bchC gene encodes a 33-kDa protein that is less hydrophobic than integral membrane proteins of R. capsulatus, although there are hydrophobic segments that could in principle interact with a lipid membrane. Results of S1 nuclease protection and primer extension experiments show that a 5' mRNA end is positioned within the cloned segment, and that this 5' end maps to sequences with significant sequence similarity to the previously characterized puf operon promoter region.
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PMID:Promoter mapping and nucleotide sequence of the bchC bacteriochlorophyll biosynthesis gene from Rhodobacter capsulatus. 255 68

In Rhodospirillum rubrum, the genes coding for the alpha and beta polypeptides of the B880 antenna (pufA,B) and the L and M polypeptides of the photoreaction center (pufL,M) are clustered on operon puf. In oxygen-limited cells, the puf mRNA is present as species of 2561, 640, and 617 nucleotides. Aerated cells contain only traces of these mRNAs. The large mRNA encodes the alpha,beta, L, and M polypeptides, whereas the small mRNAs encode only alpha and beta. S1 nuclease protection mapping showed these transcripts to have a common 5' end, immediately downstream of a region of dyad symmetry and at 166 nucleotides upstream of the initiation codon of pufB. The 3' termini of the small transcripts are located in the intercistronic region between pufA and pufL, downstream of another region of dyad symmetry. This region is highly conserved in Rhodospirillum rubrum, Rhodobacter capsulatus, and Rhodobacter sphaeroides and shares 61% sequence similarity with the repetitive extragenic palindromic sequences of Escherichia coli. The slightly heterogeneous 3' termini of the large transcript are downstream of a region of dyad symmetry characteristic of rho-independent transcription termination. Following a shift from oxygen-limited to aerated conditions, the pufL,M and the pufA,B mRNAs decayed with respective half-lives of 9 and 20 min. These high relative stabilities, attributed to secondary structure, are in accord with the mole ratio (2:1) of the pufA,B/pufL,M messages. While the differential expression of alpha,beta/L,M congruent to 15 is thought to be due, in part, to this relative stability, the main factor may be a more efficient translation initiation for pufA,B than for pufL,M.
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PMID:Structure and expression of the puf operon messenger RNA in rhodospirillum rubrum. 313 24