High impact information on PPA1

• Mutations at the corresponding sites in the VMA11 and VMA16 genes of S. cerevisiae, which encode the c' and c" subunits, did not confer resistance to the drugs [1].
• Limited proteolysis of epitope-tagged c" (Vma16p) indicated that the N terminus is located on the cytoplasmic face of the vacuole, whereas the C terminus is located within the vacuole [2].
• To obtain information about the topology of Vma16p, labeling of single cysteine-containing mutants using the membrane-permeable reagent 3-(N-maleimidylpropionyl)biocytin (MPB) and the -impermeable reagent 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid (AMS) was tested [3].
• Both the Cys-less form of Vma16p and eight single cysteine-containing mutants retained greater than 80% of wild type levels of activity [3].
• In addition, a hemagglutinin epitope tag introduced into the C terminus of Vma16p was recognized by an anti-hemagglutinin antibody in intact vacuolar membranes, suggesting a cytoplasmic orientation for the C terminus [3].

Biological context of PPA1

• Cells disrupted for the VMA16 gene displayed the same phenotypes as those lacking either Vma3p or Vma11p; the mutant cells lost V-ATPase activity and failed to assemble V-ATPase subunits onto the vacuolar membrane [4].

Anatomical context of PPA1

• Vacuoles isolated from the strain expressing Vma16p-Delta TM1 showed V-ATPase activity and proton transport greater than 80% relative to wild type and displayed wild type levels of subunits A and a, suggesting normal assembly of the V-ATPase complex [3].

Other interactions of PPA1

• Surprisingly, loss-of-function mutations of either Vma11p Glu145 or Vma16p Glu108 resulted in a higher degree of assembly of the V1 subunits onto the V0 subcomplex in the vacuolar membrane [4].
• The anti-HA epitope antibody inhibited both the ATP-dependent proton uptake and the ATPase activities of the Vma16p-HA and Vma7p-HA containing complexes, in intact vacuoles and in the detergent-solubilized enzyme [5].
• Towards this end we used HA to tag subunits Vma7p, Vma10p and Vma16p, which are assumed to represent, respectively, the shaft, stator and turbine of the enzyme, and used them to supplement the corresponding yeast V-ATPase null mutants [5].

Analytical, diagnostic and therapeutic context of PPA1

• Epitope-tagged Vma11p and Vma16p were detected on the vacuolar membrane by immunofluorescence microscopy [4].

References