Characterization of non-dominant lethal mutations in the yeast plasma membrane H+-ATPase gene

Site-directed mutants of yeast ATPase were previously studied after introdu ction of mutant alleles into a yeast strain where these alleles were consti tutively expressed white the expression of the wild-type chromosomal ATPase gene was turned off. As a functional H+ pump is essential, strong selectiv e pressure leads to the accumulation of revertants during growth of cells h arboring variants with low activity. Thus, constitutive expression of the m utant gene can select phenotypes which reflect events such as gene conversi on or reversion. We have therefore re-evaluated the phenotypes of non-domin ant lethal alleles in an alternative set of conditional expression systems. We show that eight of II previously described site-directed mutations beha ve as recessive lethal alleles. (C) 1999 Elsevier Science B.V. Ali rights r eserved.