The ARG11 Gene of Saccharomyces cerevisiae Encodes a Mitochondrial Integral Membrane Protein Required for Arginine Biosynthesis

Abstract

Prototype strain MG409 (arg11-1) is a severe arginine bradytroph with greatly reduced ornithine and arginine pools, although all known enzymes required for arginine biosynthesis are functional. To identify the function required for normal arginine production impaired in MG409, we have cloned, sequenced, and performed a first molecular characterization of ARG11.We show that the ARG11 open reading frame encodes a putative 292-residue protein with a predicted molecular mass of 31.5 kDa. Sequence similarities, a tripartite organization, and six potential hydrophobic transmembrane spans suggest that Arg11p belongs to the mitochondrial integral inner membrane carrier family. We have used immuno-Western blotting and hemagglutinin epitope-tagged derivatives of Arg11p, Arg8p (a mitochondrial matrix marker), and Arg3p (a cytosolic marker) to demonstrate that Arg11p is confined to the mitochondria and behaves like an integral membrane protein.A deletion created in ARG11 causes the same arginineleaky behavior as the original arg11-1 mutation, which yields a premature stop codon at residue 266. Arg11p thus appears to fulfill a partially redundant function requiring its 27 carboxyl-terminal amino acids. As a working hypothesis, we propose that Arg11p participates in the export of matrix-made ornithine into the cytosol.

Gcn4p, a Master Regulator of Gene Expression, Is Controlled at Multiple Levels by Diverse Signals of Starvation and Stress

“…3), proteins involved in the transport of small molecules between the cytosol and mitochondria (71). Mutation of one of these genes, ARG11/ORT1, confers leaky arginine auxotrophy (14), consistent with its importance in arginine biosynthesis.…”

Recruitment of the ArgR/Mcm1p repressor is stimulated by the activator Gcn4p: A self-checking activation mechanism

“…ARG11 encodes a mitochondrial membrane protein required for efficient arginine biosynthesis, most likely functioning in export of ornithine from mitochondria to the cytoplasm (20). Thus, arg11⌬ cells have greatly reduced arginine pools (21) and exhibit fully derepressed levels of arginine biosynthetic enzymes regulated by ArgR͞Mcm1p in medium lacking arginine (22).…”

Phylogenetic Classification of the Mitochondrial Carrier Family ofSaccharomyces cerevisiae

“…Moreover, some genes coding for yeast proteins of unknown function have been identified as members of the MCF, such as the MRS3 and MRS4 genes encoding suppressors of mitochondrial splicing defect (Wiesenberger et al, 1991), the ACR1 gene encoding a protein which is essential for acetyl CoA synthetase (Fernández et al, 1994), the RIM2 gene encoding a protein that is essential for mitochondrial DNA metabolism and rescues the respiratory defect of pif1 and mrs2 null mutants (Demolis et al, 1993;Van Dyck et al, 1995) and the ARG11 gene encoding a putative carrier required for arginine biosynthesis (Crabeel et al, 1996).…”