INDUCTION OF MAJOR HEAT-SHOCK PROTEINS OF SACCHAROMYCES-CEREVISIAE, INCLUDING PLASMA-MEMBRANE HSP30, BY ETHANOL LEVELS ABOVE A CRITICAL THRESHOLD

Many of the changes induced in yeast by sublethal yet stressful amount s of ethanol are the same as those resulting from sublethal heat stres s. They include an inhibition of fermentation, increased induction of petites and stimulation of plasma membrane ATPase activity. Ethanol, a t concentrations (4-10%, v/v) that affect growth and fermentation rate s, is also a potent inducer of heat-shock proteins including those mem bers of the Hsp70 protein family induced by heat shock. This induction occurs above a threshold level of about 4% ethanol, although differen t heat-shock proteins and heat-shock gene promoters are optimally indu ced at different higher ethanol levels. In addition ethanol (6-8%) cau ses the same two major changes to integral plasma-membrane protein com position that result from a sublethal heat stress, reduction in levels of the plasma membrane ATPase protein and acquisition of the plasma m embrane heat-shock protein Hsp30.