The Riboflavin Transporter RibU in Lactococcus lactis : Molecular Characterization of Gene Expression and the Transport Mechanism
Open Access
- 15 April 2006
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 188 (8), 2752-2760
- https://doi.org/10.1128/jb.188.8.2752-2760.2006
Abstract
This study describes the characterization of the riboflavin transport protein RibU in the lactic acid bacterium Lactococcus lactis subsp. cremoris NZ9000. RibU is predicted to contain five membrane-spanning segments and is a member of a novel transport protein family, not described in the Transport Classification Database. Transcriptional analysis revealed that ribU transcription is downregulated in response to riboflavin and flavin mononucleotide (FMN), presumably by means of the structurally conserved RFN (riboflavin) element located between the transcription start site and the start codon. An L. lactis strain carrying a mutated ribU gene exhibits altered transcriptional control of the riboflavin biosynthesis operon ribGBAH in response to riboflavin and FMN and does not consume riboflavin from its growth medium. Furthermore, it was shown that radiolabeled riboflavin is not taken up by the ribU mutant strain, in contrast to the wild-type strain, directly demonstrating the involvement of RibU in riboflavin uptake. FMN and the toxic riboflavin analogue roseoflavin were shown to inhibit riboflavin uptake and are likely to be RibU substrates. FMN transport by RibU is consistent with the observed transcriptional regulation of the ribGBAH operon by external FMN. The presented transport data are consistent with a uniport mechanism for riboflavin translocation and provide the first detailed molecular and functional analysis of a bacterial protein involved in riboflavin transport.Keywords
This publication has 37 references indexed in Scilit:
- Multivitamin production in Lactococcus lactis using metabolic engineeringMetabolic Engineering, 2003
- The Ascorbate Transporter of Escherichia coliJournal of Bacteriology, 2003
- Conservation of the Biotin Regulon and the BirA Regulatory Signal in Eubacteria and ArchaeaGenome Research, 2002
- Predicting transmembrane protein topology with a hidden markov model: application to complete genomesJournal of Molecular Biology, 2001
- Structural and functional analysis of the riboflavin synthesis genes encoding GTP cyclohydrolase II (ribA), DHBP synthase (ribBA), riboflavin synthase (ribC), and riboflavin deaminase/reductase (ribD) fromHelicobacter pyloristrain P1FEMS Microbiology Letters, 2000
- The kdgRKAT operon of Bacillus subtilis:detection of the transcript and regulation by the kdgR and ccpA genesMicrobiology, 1998
- Quorum sensing-controlled gene expression in lactic acid bacteriaJournal of Biotechnology, 1998
- Gapped BLAST and PSI-BLAST: a new generation of protein database search programsNucleic Acids Research, 1997
- A general system for generating unlabelled gene replacements in bacterial chromosomesMolecular Genetics and Genomics, 1996
- Characterization of the nisin gene cluster nisABTCIPR of Lactococcus lactisEuropean Journal of Biochemistry, 1993