Auxin-induced differential sensitivity of the H+-ATPase in plasma membrane subfractions from tobacco cells

Plasmamembrane vesicles from suspension cultured tobacco cells were fractionated by counter-current phase partitioning. The subfractions exhibited identical biochemical characteristics and differed mainly by their sidedness. In addition, fluorescence polarization experiments indicated slight fluidity or order differences. These characteristics remained unchanged when cells were treated with auxin, prior to membrane purification. The sensitivity to auxin of the Hf-ATPase catalysed proton translocation was investigated in plasma membrane subfractions. Identical sensitivity was measured in all subfractions from control cells. After auxin treatment of cells, a dramatic increase in the sensitivity was observed in one subfraction. Results are discussed in relation to the recent report of an auxin-induced clustering of the putative auxin-receptor (Diekmann et al., Proc. Natl. Acad. Sci. USA 92, 3425-3429, 1995). (C) 1996 Academic Press, Inc.