The ability of a vacuolar H(+)-ATPase (V-ATPase) subunit homolog (subunit A) from plants to rescue the vma mutant phenotype of yeast was investigated as a first step towards investigating the structure and function of plant subunits in molecular detail. Heterologous expression of cotton cDNAs encoding near-identical isoforms of subunit A in mutant vma1 delta yeast cells successfully rescued the mutant vma phenotype, indicating that subunit A of plants and yeast have retained elements essential to V-ATPases during the course of evolution. Although vacuoles become acidified, the plant-yeast hybrid holoenzyme only partially restored V-ATPase activity (approximately 60%) in mutant yeast cells. Domain substitution of divergent N- or C-termini only slightly enhanced V-ATPase activity, whereas swapping both domains acted synergistically, increasing coupled ATP hydrolysis and proton translocation by approximately 22% relative to the native plant subunit. Immunoblot analysis indicated that similar amounts of yeast, plant or plant-yeast chimeric subunits are membrane-bound. These results suggest that subunit A terminal domains contain structural information that impact V-ATPase structure and function.

• PMID: 10205905
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Journal Article | Research Support, U.S. Gov't, Non-P.H.S.

Authors

Kim W, Wan CY, Wilkins TA

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