The yeast mitochondrial ADP/ATP carrier functions as a monomer in mitochondrial membranes.

TitleThe yeast mitochondrial ADP/ATP carrier functions as a monomer in mitochondrial membranes.
Publication TypeJournal Article
Year of Publication2007
AuthorsBamber, L, Harding, M, Monné, M, Slotboom, D-J, Kunji, ERS
JournalProc Natl Acad Sci U S A
Volume104
Issue26
Pagination10830-4
Date Published2007 Jun 26
ISSN1091-6490
KeywordsAdenine Nucleotides, Kinetics, Mesylates, Mitochondrial ADP, ATP Translocases, Mitochondrial Membranes, Protein Conformation, Protein Structure, Quaternary, Saccharomyces cerevisiae Proteins, Sulfhydryl Reagents
Abstract

Mitochondrial carriers are believed widely to be dimers both in structure and function. However, the structural fold is a barrel of six transmembrane alpha-helices without an obvious dimerisation interface. Here, we show by negative dominance studies that the yeast mitochondrial ADP/ATP carrier 2 from Saccharomyces cerevisiae (AAC2) is functional as a monomer in the mitochondrial membrane. Adenine nucleotide transport by wild-type AAC2 is inhibited by the sulfhydryl reagent 2-sulfonatoethyl-methanethiosulfonate (MTSES), whereas the activity of a mutant AAC2, devoid of cysteines, is unaffected. Wild-type and cysteine-less AAC2 were coexpressed in different molar ratios in yeast mitochondrial membranes. After addition of MTSES the residual transport activity correlated linearly with the fraction of cysteine-less carrier present in the membranes, and so the two versions functioned independently of each other. Also, the cysteine-less and wild-type carriers were purified separately, mixed in defined ratios and reconstituted into liposomes. Again, the residual transport activity in the presence of MTSES depended linearly on the amount of cysteine-less carrier. Thus, the entire transport cycle for ADP/ATP exchange is carried out by the monomer.

DOI10.1073/pnas.0703969104
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
Citation Key10.1073/pnas.0703969104
PubMed ID17566106
PubMed Central IDPMC1891095
Grant ListMC_U105663139 / / Medical Research Council / United Kingdom