Guanine nucleotide regulation of adenylate cyclase in permeabilized cells of Saccharomyces cerevisiae

Abstract

Adenylate cyclase in permeabilized cells of Saccharomyces cerevisiae was examined. Among various permeabilization procedures, including organic solvents, detergents and other reagents, dimethylsulfoxide (DMSO) and digitonin treatments resulted in the highest recovery of adenylate cyclase activity. Incubation of cells at 30°C with digitonin at 0.01% to 0.1%, or DMSO at 20% to 40% for 15 to 30 min gave optimal adenylate cyclase activity. The enzyme activity in digitonin-permeabilized cells could be supported only by Mn 2+, whereas Mg 2+ with or without guanine nucleotides did not support cyclase actiivty. DMSO-permeabilized cells exhibit efficient Mn 2+- and Mg 2+ / Gpp[NH]p-dependent stimulation. Furthermore, digitonin added to yeast membranes at a 1:50 detergent to protein ratio (w / w) abolishes guanyl nucleotide regulation without significantly affecting the Mn 2+-supported cyclase activity. The superiority of DMSO is further supported by the fact that recovery of adenylate cyclase activity is better in the DMSO-treated cells than in the digitonin-treated cells. DMSO most probably causes less disturbance of the fabric of the native cell. We conclude that digitonin, but not DMSO, uncouples the catalytic unit of adenylate cyclase from the regulatory GTP binding ( ras) proteins.