title: Translational control of puf operon expression in Rhodobacter sphaeroides 2.4.1.
abstract: The puf operon of Rhodobacter sphaeroides 2.4.1 encode the beta- and alpha-polypeptides of the B875 complex, the L and M polypeptides of the reaction centre and the pufX gene product. A previous report from the authors' laboratory indicated the potential existence of a 20-codon open reading frame (orfK, now designated pufK) located immediately upstream of the pufB structural gene. It is now demonstrated that pufK is translated in vivo and that the specific levels or nature of the rare codons within pufK affect the expression of pufK. Using a series of pufK-specific mutations, both in trans as lacZ translational fusions and incorporated into the genome in single copy, evidence has been obtained that translation initiation through pufK may be essential to translation of pufB. Further, the abundance, quality and distribution of rare codons within pufK may serve to 'gate' the entry of ribosomes at pufB. The data also suggest that translation of pufB is uncoupled from that of pufA, with the latter capable of being produced in excess of the former. It is also revealed that the secondary structure at the 5' end of the large and small puf transcripts may play a role in mRNA stability and that stability of the small puf transcript is independent of translation.
authors: Department of Microbiology and Molecular Genetics, University of Texas at Houston-Medical School 77225, USA.
authors: L
authors: L
authors: Gong
authors: S
authors: S
authors: Kaplan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D003062:Codon; D017931:DNA Primers; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D009876:Operon; D045322:Photosynthetic Reaction Center Complex Proteins / Q000096:biosynthesis* / Q000235:genetics; D010957:Plasmids; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; D003062:Codon; D017931:DNA Primers; D045322:Photosynthetic Reaction Center Complex Proteins; C101051:PufK protein, Rhodobacter sphaeroides; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D001616:beta-Galactosidase