The putative monocarboxylate permeases of the yeast Saccharomyces cerevisiae do not transport monocarboxylic acids across the plasma membrane

Abstract

We have characterized the monocarboxylate permease family of Saccharomyces cerevisiae comprising five proteins. We could not find any evidence that the monocarboxylate transporter-homologous (Mch) proteins of S. cerevisiae are involved in the uptake or secretion of monocarboxylates such as lactate, pyruvate or acetate across the plasma membrane. A yeast mutant strain deleted for all five MCH genes exhibited no growth defects on monocarboxylic acids as the sole carbon and energy sources. Moreover, the uptake and secretion rates of monocarboxylic acids were indistinguishable from the wildtype strain. Additional deletion of the JEN1 lactate transporter gene completely blocked uptake of lactate and pyruvate. However, uptake of acetate was not even affected after the additional deletion of the gene YHL008c, which had been proposed to code for an acetate transporter. The mch1-5 mutant strain showed strongly reduced biomass yields in aerobic glucose-limited chemostat cultures, pointing to the involvement of Mch transporters in mitochondrial metabolism. Indeed, intracellular localization studies indicated that at least some of the Mch proteins reside in intracellular membranes. However, pyruvate uptake into isolated mitochondria was not affected in the mch1-5 mutant strain. It is concluded that the yeast monocarboxylate transporter-homologous proteins perform other functions than do their mammalian counterparts.

Effect of 21 Different Nitrogen Sources on Global Gene Expression in the YeastSaccharomyces cerevisiae

“…As expected, these include ARO9 and ARO10, coding, respectively, for the transaminase and the decarboxylase involved in degrading these amino acids (62,133) and known to be induced by aromatic amino acids via the Aro80 transcription factor (62). Among the three other genes displaying a similar expression profile, ESBP6 encodes a mitochondrial protein sharing sequence similarities with monocarboxylic acid transporters, but its function remains unknown (87). Another such gene is YDR379C-A, a gene adjacent to ARO10/YDR380W and separated from it by 701 bp.…”

“…The involvement of multiple, partially redundant enzymes displaying overlapping substrate specificities very likely explains why classical genetics-based approaches have not allowed effective dissection of the catabolic pathways of group B amino acids, in marked contrast to their successful use in dissecting amino acid anabolic pathways (69). We have also extended the ARO regulon involved in amino acid catabolism to two other genes, one of which (ESBP6/MCH3) encodes a putative transporter that localizes to the inner mitochondrial membrane (87). As Aro9 and Aro10 are cytoplasmic enzymes (61), Mch3 might be responsible for the transport of aldehydes into mitochondria, where several alcohol dehydrogenase activities have been detected (42).…”

Identity of a Plasmodium lactate/H+ symporter structurally unrelated to human transporters

“…1). Jen1 is unrelated to MCT-like proteins, of which the yeast genome encodes five members, yet none of these facilitates lactate transport 20 . These and the lactate-impermeable Plasmodium MCT-type proteins could suggest that MCTs assumed lactate transport function later in evolution.…”

Transport and cytotoxicity of the anticancer drug 3-bromopyruvate in the yeast Saccharomyces cerevisiae

“…Additionally, the yeast genome encodes five members of the Monocarboxylate Porter (MCP) Family (De Hertogh et al 2002), but their role in importing monocarboxylic acids has not been proven (Makuc et al 2001;Reihl and Stolz 2005). Casal et al (Casal et al 1999).…”