3.A.2.2.3
H+-translocating V-type ATPase. The d-subunit couples ATP hydrolysis to H+ transport (Owegi et al., 2006). The a subunit (Vph1p) most likely has an 8 TMS topology (Kartner et al. 2013; Knight and Behm 2012). Structures for three
rotational states show ten proteolipid subunits in the c-ring, setting the ATP:H+ ratio for proton
pumping. Long tilted TMSs in
the a-subunit interact with the c-ring. V-ATPase's membrane sector, Vo, has been implicated in functions including
membrane fusion and neurotransmitter release. Couoh-Cardel et al. 2016 reported that the purified V-ATPase c subunit ring (c-ring) forms dimers mediated by the c subunits'
cytoplasmic loops. Electrophysiological measurements of the c-ring reconstituted into a planar lipid
bilayer revealed a large unitary conductance of ~8.3 nS. A role of the
c-ring in membrane fusion and neuronal communication was suggested (Couoh-Cardel et al. 2016). The three different maps reveal the conformational
changes that occur to couple rotation in the symmetry-mismatched soluble catalytic region to the
membrane-bound proton-translocating region. Almost all of the subunits undergo
conformational changes during the transitions between these three rotational states (Zhao et al. 2015). The structures
of these states provide direct evidence that deformation during rotation enables the smooth
transmission of power through rotary ATPases.
Increases in glucose stimulate V-ATPase assembly and activity while glucose deprivation triggers rapid V-ATPase disassembly and inactivation in
yeast. However, the opposite phenomenon is observed in mammalian
cells, specifically that V-ATPase assembly and activation increases when
glucose is lost (Parra and Hayek 2018). The 3.5 Å resolution cryoEM structure of the lipid nanodisc-reconstituted Vo proton channel, captured in a physiologically relevant
autoinhibited state, revealing the residues that constitute the proton
pathway at the interface of the proteolipid ring and subunit a has been solved (Roh et al. 2018). The chemical basis of transmembrane proton transport was proposed. Roh et al. 2018 discovered that the C terminus of the assembly factor Voa1 (TC# 9.B.206.2.1)) is an
integral component of the mature Vo. Voa1's C-terminal transmembrane alpha
helix is bound inside the proteolipid ring, where it contributes to the
stability of the complex. The structure rationalizes possible mechanisms
by which mutations in human Vo can result in disease phenotypes (Roh et al. 2018). The cytosolic N-terminal domain of the V-ATPase a-subunits is a regulatory hub targeted by multiple signals (Tuli and Kane 2023).
An arginine residue (Arg-735) in transmembrane helix 7 (TMS7) of subunit a of the yeast ATPase is known to be essential
for proton translocation. Arginine residues are usually assumed to
'snorkel' toward the protein surface when exposed to a hydrophobic
environment. However, Hohlweg et al. 2018 obtained evidence for
the formation of a transient, membrane-embedded cation-π interaction in
TM7 between Arg-735 and two highly conserved nearby aromatic residues,
Tyr-733 and Trp-737. They proposed a mechanism by which the transient,
membrane-embedded cation-π complex provides the necessary energy to keep
the charged side chain of Arg-735 within the hydrophobic membrane. Such
cation-π interactions may define a general mechanism to retain charged
amino acids in a hydrophobic membrane environment (Hohlweg et al. 2018). A 2.7-A cryo-EM structure of the yeast Vo proton channel revealed the
location of ordered water molecules along the proton path, details of
specific protein-lipid interactions, and the architecture of the
membrane scaffold protein (Roh et al. 2020) as well as a state of Vo showing the c-ring rotated by ~14 degrees. Two rotary states are in thermal equilibrium and depict how the protonation state of essential glutamic acid residues couples water-mediated proton transfer with c-ring rotation. Resuts suggest a mechanism for inhibition of passive proton transport as observed for free Vo that is generated as a result of V-ATPase regulation by reversible disassembly in vivo (Roh et al. 2020). Vacuolar H+-ATPase dysfunction rescues intralumenal vesicle cargo sorting in yeast lacking PI(3,5)P2 or Doa4 (Wilson et al. 2021). The V-ATPase a-subunit is a two-domain protein containing a C-terminal transmembrane domain responsible for proton transport and an N-terminal cytosolic domain that is a regulatory hub, integrating environmental inputs to regulate assembly, localization, and V-ATPase activity. S. cerevisiae encodes two organelle-specific a-isoforms, Stv1 in the Golgi and Vph1 in the vacuole (Tuli and Kane 2023). The significance of the plasma membrane H+-ATPase and V-ATPase for growth and pathogenicity in pathogenic fungi has been discussed (Yang and Peng 2023).
|
Accession Number: | P22203 |
Protein Name: | VMA4 aka VATE aka VAT5 aka YOR332W |
Length: | 233 |
Molecular Weight: | 26471.00 |
Species: | Saccharomyces cerevisiae (Baker's yeast) [4932] |
Location1 / Topology2 / Orientation3: |
Vacuole membrane1 / Peripheral membrane protein2 |
Substrate |
hydron |
---|
DIP: |
DIP-4595N
|
RefSeq: |
NP_014977.1
|
Entrez Gene ID: |
854509
|
Pfam: |
PF01991
|
KEGG: |
sce:YOR332W
|
|
[1] “The 31-kDa polypeptide is an essential subunit of the vacuolar ATPase in Saccharomyces cerevisiae.” Foury F. et.al. 2145285
[2] “Sequence of 29 kb around the PDR10 locus on the right arm of Saccharomyces cerevisiae chromosome XV: similarity to part of chromosome I.” Parle-McDermott A.G. et.al. 8896263
[3] “The nucleotide sequence of Saccharomyces cerevisiae chromosome XV.” Dujon B. et.al. 9169874
[4] “Isolation of vacuolar membrane H(+)-ATPase-deficient yeast mutants; the VMA5 and VMA4 genes are essential for assembly and activity of the vacuolar H(+)-ATPase.” Ho M.N. et.al. 8416931
[5] “Resolution of subunit interactions and cytoplasmic subcomplexes of the yeast vacuolar proton-translocating ATPase.” Tomashek J.J. et.al. 8626613
[6] “Characterization of a temperature-sensitive yeast vacuolar ATPase mutant with defects in actin distribution and bud morphology.” Zhang J.W. et.al. 9660816
[7] “Skp1 forms multiple protein complexes, including RAVE, a regulator of V-ATPase assembly.” Seol J.H. et.al. 11283612
[8] “Global analysis of protein localization in budding yeast.” Huh W.-K. et.al. 14562095
[9] “Global analysis of protein expression in yeast.” Ghaemmaghami S. et.al. 14562106
[10] “Defined sites of interaction between subunits E (Vma4p), C (Vma5p), and G (Vma10p) within the stator structure of the vacuolar H(+)-ATPase.” Jones R.P.O. et.al. 15751969
[11] “Mutational analysis of the stator subunit E of the yeast V-ATPase.” Owegi M.A. et.al. 15718227
[12] “A multidimensional chromatography technology for in-depth phosphoproteome analysis.” Albuquerque C.P. et.al. 18407956
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[...more]
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1: MSSAITALTP NQVNDELNKM QAFIRKEAEE KAKEIQLKAD QEYEIEKTNI VRNETNNIDG
61: NFKSKLKKAM LSQQITKSTI ANKMRLKVLS AREQSLDGIF EETKEKLSGI ANNRDEYKPI
121: LQSLIVEALL KLLEPKAIVK ALERDVDLIE SMKDDIMREY GEKAQRAPLE EIVISNDYLN
181: KDLVSGGVVV SNASDKIEIN NTLEERLKLL SEEALPAIRL ELYGPSKTRK FFD