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A novel role for the yeast protein kinase Dbf2p in vacuolar H⁺-ATPase function and sorbic acid stress tolerance

Vasso Makrantoni^1,

¹ Centre for Biomolecular Sciences, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
² Division of Gene Regulation and Expression, College of Life Sciences, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK

Correspondence
Peter J. Coote
pjc5{at}st-andrews.ac.uk

In Saccharomyces cerevisiae, the serine-threonine protein kinase activity of Dbf2p is required for tolerance to the weak organic acid sorbic acid. Here we show that Dbf2p is required for normal phosphorylation of the vacuolar H⁺-ATPase (V-ATPase) A and B subunits Vma1p and Vma2p. Loss of V-ATPase activity due to bafilomycin treatment or deletion of either VMA1 or VMA2 resulted in sorbic acid hypersensitivity and impaired vacuolar acidification, phenotypes also observed in both a kinase-inactive dbf2 mutant and cells completely lacking DBF2 (dbf2). Crucially, VMA2 is a multicopy suppressor of both the sorbic acid-sensitive phenotype and the impaired vacuolar-acidification defect of dbf2 cells, confirming a functional interaction between Dbf2p and Vma2p. The yeast V-ATPase is therefore involved in mediating sorbic acid stress tolerance, and we have shown a novel and unexpected role for the cell cycle-regulated protein kinase Dbf2p in promoting V-ATPase function.

Present address: Division of Gene Regulation and Expression, College of Life Sciences, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK.