Functional analysis of subunit e of the F1Fo-ATP synthase of the yeast Saccharomyces cerevisiae: importance of the N-terminal membrane anchor region.
Mitochondrial F1Fo-ATP synthase complexes do not exist as physically independent entities but rather form dimeric and possibly oligomeric complexes in the inner mitochondrial membrane. Stable dimerization of two F1Fo-monomeric complexes involves the physical association of two membrane-embedded Fo-sectors. Previously, formation of the ATP synthase dimeric-oligomeric network was demonstrated to play a critical role in modulating the morphology of the mitochondrial inner membrane. In Saccharomyces cerevisiae, subunit e (Su e) of the Fo-sector plays a central role in supporting ATP synthase dimerization. The Su e protein is anchored to the inner membrane via a hydrophobic region located at its N-terminal end. The hydrophilic C-terminal region of Su e resides in the intermembrane space and contains a conserved coiled-coil motif. In the present study, we focused on characterizing the importance of these regions for the function of Su e. We created a number of C-terminal-truncated derivatives of the Su e protein and expressed them in the Su e null yeast mutant. Mitochondria were isolated from the resulting transformant strains, and a number of functions of Su e were analyzed. Our results indicate that the N-terminal hydrophobic region plays important roles in the Su e-dependent processes of mitochondrial DNA maintenance, modulation of mitochondrial morphology, and stabilization of the dimer-specific Fo subunits, subunits g and k. Furthermore, we show that the C-terminal coiled-coil region of Su e functions to stabilize the dimeric form of detergent-solubilized ATP synthase complexes. Finally, we propose a model to explain how Su e supports the assembly of the ATP synthase dimers-oligomers in the mitochondrial membrane.
Everard-Gigot
Valerie
V
Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA.
Dunn
Cory D
CD
Dolan
Brigid M
BM
Brunner
Susanne
S
Jensen
Robert E
RE
Stuart
Rosemary A
RA
D004272:DNA, Mitochondrial / Q000378:metabolism; D019281:Dimerization; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004272:DNA, Mitochondrial; D029701:Saccharomyces cerevisiae Proteins; D025261:Mitochondrial Proton-Translocating ATPases; C102550:TIM11 protein, S cerevisiae