All higher plants possess highly specific binding sites for fusicoccin, a metabolite of the fungus Fusicoccum amygdali Del. These sites are harboured in the plasma membranes and formed by a 14-3-3 protein dimer associated with the C-terminal autoinhibitory domain of H + -ATPase. We considered the fusicoccin binding to plasma membranes to be an indicator of complexation between the 14-3-3 dimer and H + -ATPase, we assessed the effect of cold stress on the interaction of these proteins in suspension-cultured sugar beet cells and protoplasts derived from these cells. In both objects, upon lowering the temperature to 0^4³C, a portion of the cytoplasmic 14-3-3 proteins became associated with the plasma membrane, which showed an increasing amount of ATPase/14-3-3 complexes and enhanced ATPase activity. Association between ATPase and 14-3-3 resulted in a several-fold rise in the H + efflux from protoplasts and intact cells. We suppose that regulation of the H + pumping under changing external conditions may be based on the interaction between H + -ATPase and the 14-3-3 proteins.z 1999 Federation of European Biochemical Societies.
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