The yeast F(1)F(0)-ATP synthase: analysis of the molecular organization of subunit g and the importance of a conserved GXXXG motif.
The F(1)F(0)-ATP synthase enzyme is located in the inner mitochondrial membrane, where it forms dimeric complexes. Dimerization of the ATP synthase involves the physical association of the neighboring membrane-embedded F(0)-sectors. In yeast, the F(0)-sector subunits g and e (Su g and Su e, respectively) play a key role in supporting the formation of ATP synthase dimers. In this study we have focused on Su g to gain a better understanding of the function and the molecular organization of this subunit within the ATP synthase complex. Su g proteins contain a GXXXG motif (G is glycine, and X is any amino acid) in their single transmembrane segment. GXXXG can be a dimerization motif that supports helix-helix interactions between neighboring transmembrane segments. We demonstrate here that the GXXXG motif is important for the function and in particular for the stability of Su g within the ATP synthase. Using site-directed mutagenesis and cross-linking approaches, we demonstrate that Su g and Su e interact, and our findings emphasize the importance of the membrane anchor regions of these proteins for their interaction. Su e also contains a conserved GXXXG motif in its membrane anchor. However, data presented here would suggest that an intact GXXXG motif in Su g is not essential for the Su g-Su e interaction. We suggest that the GXXXG motif may not be the sole basis for a Su g-Su e interaction, and possibly these dimerization motifs may enable both Su g and Su e to interact with another mitochondrial protein.
Saddar
Sonika
S
Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53233, USA.
Stuart
Rosemary A
RA
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D005998:Glycine / Q000737:chemistry; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry* / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D003432:Cross-Linking Reagents; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases; D003545:Cysteine; D005998:Glycine