High impact information on VMA2

• Vacuoles isolated from cells bearing the vat2 null allele were completely devoid of vacuolar ATPase activity [1].
• The vacuolar acidification-defective vat2 mutant exhibited normal zymogen activation but displayed a minor defect in vacuolar protein sorting [1].
• For photochemical cross-linking, unique cysteine residues were introduced into the yeast V-ATPase B subunit at sites that were localized based on molecular modeling using the crystal structure of the mitochondrial F(1) domain [2].
• To investigate residues involved in the formation of the noncatalytic nucleotide binding sites of the vacuolar proton-translocating adenosine triphosphatase (V-ATPase), cysteine scanning mutagenesis of the VMA2 gene that encodes the B subunit in yeast was performed [3].
• Replacement of the single endogenous cysteine residue at position 188 gave rise to a Cys-less form of the B subunit (Vma2p) which had near wild-type levels of activity and which was used in the construction of 16 single cysteine-containing mutants [3].

Biological context of VMA2

• Cloning of structural genes for the three subunits of the H+-ATPase (VMA1, VMA2, and VMA3) and their nucleotide sequence determination have been accomplished, which provide greater advantages for molecular biological studies on the structure-function relationship and biogenesis of the enzyme complex [4].
• However, its deletion in cells lacking the vacuolar ATPase subunit Vma2p leads to loss of viability, suggesting that Tlg2p is involved in endocytosis [5].
• Mutations at two residues postulated to be contributed by Vma2p to the catalytic site (R381S and Y352S) resulted in a complete loss of ATPase activity and proton transport, with the former having a partial effect on V-ATPase assembly [6].
• Both genes are interrupted by introns, two in vma1 and four in vma2 [7].

Associations of VMA2 with chemical compounds

• None of the mutations in either the putative adenine binding pocket nor the P-loop region had any effect on the ability of Vma2p to correctly fold nor on the V-ATPase to correctly assemble [6].

Physical interactions of VMA2

• Yeast two-hybrid data indicate that Vma1p and Vma2p interact with each other and that Vma4p interacts with itself [8].

Other interactions of VMA2

• No alleles of the VAT2 or TFP1 genes (known to encode subunits of the vacuolar H(+)-ATPase) were identified in the Vph- screen [9].
• In order to investigate the influence of vacuolar pH on processing in vivo, the autoactivation of proteinase A and its processing of procarboxypeptidase Y were studied in a vma2 prb1 mutant, which is deficient in vacuolar acidification and proteinase B activity [10].

Analytical, diagnostic and therapeutic context of VMA2

• Based upon the recent x-ray structure of the mitochondrial F1 ATPase (Abrahams, J.P., Leslie, A.G., Lutter, R., and Walker, J.E. (1994) Nature 370,621-628), site-directed mutagenesis of the yeast VMA2 gene has been carried out in a strain containing a deletion of this gene [6].

References