Citrate utilization gene cluster of the Lactococcus lactis biovar diacetylactis: organization and regulation of expression.
The transport of citrate in Lactococcus lactis biovar diacetylactis is mediated by the citrate permease P. This polypeptide is encoded by the citP gene carried by plasmid pCIT264. In this report, we characterize the citP transcript, identify a cluster of two genes cotranscribed with citP and describe their post-transcriptional regulation. The transcriptional promoter is located 1500 nucleotides upstream of the citP gene and the transcriptional terminator is positioned next to the 3'-end of this gene. The DNA sequence was determined of the region upstream of the citP gene, including the promoter. Two partially overlapping open reading frames, citQ and citR were identified, which could encode polypeptides of 3.9 and 13 kDa respectively. These two genes, together with citP, constitute the cit cluster. Moreover, an IS-like element located between the cit promoter and the citQ open reading frame was identified. This element includes an open reading frame ORF1, which could encode a 33 kDa polypeptide. A translational fusion between the citP and a cat reporter gene showed that translation of citR and citP is coupled, and regulated by CitR. The cit mRNA was subjected to specific cleavage after addition of rifampicin to the bacterial cultures. We propose that expression of the cit cluster is controlled at the post-transcriptional level by mRNA processing at a putative complex secondary structure and by translational repression mediated by CitR.
López de Felipe
F
F
Centro de Investigaciones Biológicas, C.S.I.C., Velázquez, Madrid, Spain.
Magni
C
C
de Mendoza
D
D
López
P
P
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002352:Carrier Proteins; D002951:Citrates / Q000378:metabolism; D019343:Citric Acid; D004251:DNA Transposable Elements / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism; D007781:Lactoferrin / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames / Q000235:genetics; D027361:Organic Anion Transporters; D010446:Peptide Fragments / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA; D013728:Terminator Regions, Genetic / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; C112454:CitR protein, Lactococcus lactis; D002951:Citrates; D004251:DNA Transposable Elements; C112552:HLP1 protein, synthetic; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D010446:Peptide Fragments; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D019343:Citric Acid; C065431:citP protein, Lactococcus lactis; D007781:Lactoferrin