Ediger B, et al. (2009) The Tether Connecting Cytosolic (N Terminus) and Membrane (C Terminus) Domains of Yeast V-ATPase Subunit a (Vph1) Is Required for Assembly of V0 Subunit d. J Biol Chem 284(29):19522-32
Abstract: V-ATPases are molecular motors that reversibly disassemble in vivo. Anchored in the membrane is subunit a. Subunit a has a movable N-terminus that switches positions during disassembly and reassembly. Deletions were made at residues securing the N-terminus of subunit a (yeast isoform Vph1) to its membrane-bound C-terminal domain in order to understand the role of this conserved region for V-ATPase function. Shrinking of the tether made cells pH-sensitive (vma phenotype) because assembly of Vo subunit d was harmed. Subunit d did not co-immunoprecipitate with subunit a and the c-ring. Cells contained pools of V1 and Vo(-d) that failed to form V1Vo, and very low levels of V-ATPase subunits were found at the membrane. Although subunit d expression was stable and at wild-type levels, growth defects were rescued by exogenous VMA6 (subunit d). Stable V1Vo assembled after yeast cells were co-transformed with VMA6 and mutant VPH1. Tether-less V1Vo was delivered to the vacuole and active. It retained 63-71% of the wild-type activity and was responsive to glucose. Tether-less V1Vo disassembled and reassembled after brief glucose depletion and readdition. N-terminus retained binding to V1 subunits and C-terminus to phoshofructokinase. Thus, no major structural damage was generated at the N- and C-terminus of subunit a. We concluded that early steps of Vo assembly and trafficking were likely impaired by shorter tethers and rescued by VMA6.
|Status: Published||Type: Journal Article||PubMed ID: 19473972|
Topics addressed in this paper
Number of different genes curated to this paper: 4
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