Proton-translocating vacuolar-type ATPases (V-ATPases) are necessary for numerous processes in eukaryotic cells, including receptor-mediated endocytosis, protein maturation, and lysosomal acidification. In mammals, V-ATPase subunit isoforms are diffe ...
Proton-translocating vacuolar-type ATPases (V-ATPases) are necessary for numerous processes in eukaryotic cells, including receptor-mediated endocytosis, protein maturation, and lysosomal acidification. In mammals, V-ATPase subunit isoforms are differentially targeted to various intracellular compartments or tissues, but how these subunit isoforms influence enzyme activity is not clear. In the yeast Saccharomyces cerevisiae , isoform diversity is limited to two different versions of the proton-translocating subunit a: Vph1p, which is targeted to the vacuole, and Stv1p, which is targeted to the Golgi apparatus and endosomes. We show that purified V-ATPase complexes containing Vph1p have higher ATPase activity than complexes containing Stv1p and that the relative difference in activity depends on the presence of lipids. We also show that V O complexes containing Stv1p could be readily purified without attached V 1 regions. We used this effect to determine structures of the membrane-embedded V O region with Stv1p at 3.1-Å resolution, which we compare with a structure of the V O region with Vph1p that we determine to 3.2-Å resolution. These maps reveal differences in the surface charge near the cytoplasmic proton half-channel. Both maps also show the presence of bound lipids, as well as regularly spaced densities that may correspond to ergosterol or bound detergent, around the c-ring.
Organizational Affiliation:
Physical and Theoretical Chemistry Laboratory, University of Oxford, OX1 3QZ Oxford, United Kingdom.,Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.,Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; john.rubinstein@utoronto.ca.,Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada.
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