SGD Paper 
Reihl P and Stolz J (2005) The monocarboxylate transporter homolog Mch5p catalyzes riboflavin (vitamin B2) uptake in Saccharomyces cerevisiae. J Biol Chem 280(48):39809-17
Abstract: Riboflavin is a water-soluble vitamin (vitamin B2) required for the production of the flavin cofactors FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide). Mammals are unable to synthesize riboflavin and need a dietary supply of the vitamin. Riboflavin transport proteins operating in the plasma membrane thus have an important role in the absorption of the vitamin. However, their sequences remained elusive and not a single eukaryotic riboflavin transporter is known to date. Here we used a genetic approach to isolate MCH5, a Saccharomyces cerevisiae gene with homology to mammalian monocarboxylate transporters, and characterize the protein as a plasma membrane transporter for riboflavin. This conclusion is based on the suppression of riboflavin biosynthetic mutants (rib mutants) by overexpression of MCH5 and by synthetic growth defects caused by deletion of MCH5 in rib mutants. We also show that cellular processes in multiple compartments are affected by deletion of MCH5 and localize the protein to the plasma membrane. Transport experiments in S. cerevisiae and S. pombe cells demonstrate that Mch5p is a high-affinity transporter (Km = 17 microM) with a pH-optimum at pH 7.5. Riboflavin uptake is not inhibited by protonophores, does not require metabolic energy and operates by a facilitated diffusion mechanism. The expression of MCH5 is regulated by the cellular riboflavin content. This indicates that S. cerevisiae has a mechanism to sense riboflavin and avert riboflavin deficiency by increasing the expression of the plasma membrane transporter MCH5. Moreover, the other members of the MCH gene family appear to have unrelated functions.
| Status: Published | Type: Journal Article | PubMed ID: 16204239 |
Topics addressed in this paper
Number of different genes curated to this paper: 10
- To find other papers on a gene and topic, click on the colored ball in the appropriate box.
- displays other papers with information about that topic for that gene.
- displays other papers in SGD that are associated with that topic.
The topic is addressed in these papers but does not describe a specific gene or chromosomal feature.
- To go to the Locus page for a gene, click on the gene name.
| Topics | Genes linked to topics | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| ESBP6 | MCH1 | MCH2 | MCH4 | MCH5 | RIB2 | RIB3 | RIB4 | RIB5 | RIB7 | |
| Additional Literature |  | | | | | | | | ||
| Cellular Location | | |||||||||
| Cross-species Expression | | |||||||||
| Function/Process | | | ||||||||
| Genetic Interactions | | | | | | | | | | |
| Mutants/Phenotypes | | | | | | |||||
| Primary Literature | | | ||||||||
| Protein Physical Properties | | |||||||||
| Protein Sequence Features | | |||||||||
| Regulation of | | | ||||||||
| Strains/Constructs | | | | | | | ||||
| Substrates/Ligands/Cofactors | | |||||||||
