Analysis of the role(s) and molecular organization of Subunit g in yeast F1Fo‐ATP synthase

Abstract

F1Fo-ATP synthase is a molecular machine responsible for the synthesis of ATP. The F1Fo-ATP synthase consists of two oligomeric parts, the catalytic F1 sector and the membrane-embedded Fo sector. Recently it has been demonstrated that F1Fo-ATP synthase complexes exist as dimers via a physical association of two neighboring Fo-sectors. In yeast, two Fo-sector subunits, subunit g (Su g) and subunit e (Su e) play a key role in ATP synthase dimerization. Su g and Su e are not essential proteins in S. cerevisiae but play an important role in ATP synthase dimerization and in the development of cristae morphology. Su g and Su e are small hydrophobic proteins and each contains a conserved dimerization motif called GXXXG motif in their single transmembrane(TM) segment. Our previous studies were focused on the conserved GXXXG motif of Su g. We have demonstrated the importance of the GXXXG motif for the stability of Su g within the ATP synthase complex and also for the stable formation of ATP synthase dimers. We have also shown a close physical proximity between Su g and Su e; however, our data suggested that an intact GXXXG motif is not required for this interaction. We propose that both Su g and Su e may interact with other mitochondrial protein(s) via GXXXG motif. Our present work focuses on a partially conserved C-terminal region of Su g present in the mitochondrial intermembrane space. To study the potential role of Su g C-terminal region for the function(s) of Su g we have created Su g C-terminal deletion mutants in yeast. We are currently investigating the ability of these mutants to support ATP synthase dimerization and their ability to recruit a putative morphology factor important for mitochondrial morphology. Support: United States Public Health Service Grant RO1GM61573 to R. A. S.