Gramicidin S: A Potent Inhibitor of Membrane-bound Epidennal Adenosine Triphosphatase fromNicotiana tabacumL. Leaves

摘要

The effect of ionophores and tyrocidine on membrane-bound adenosine triphosphatase (ATPase) activity in epidermal cells from tobacco (Nicotiana tabacumL. cv. Samsun) leaves was investigated. Gramicidin S inhibited Mg2$-K$-ATPase activity in the epidermal membrane of tobacco leaves. Its half-maximal inhibition was found at 2.4×10−5M (under conditions of 370μg membrane protein per 2 ml reaction mixture). The degree of inhibition of the epidermal ATPase was in the following order: tyrocidine>gramicidin S>DCCD>vanadate>DES>gramicidin D, all at 10−4M. The ionophores, valinomycin, nigericin and salinomycin, inhibited the epidermal ATPase activity only slightly or not at all. The ATPase solubilized from the membrane with detergents was negligibly inhibited by gramicidin S and tyrocidine. Thus, gramicidin S acts in the manner of tyrocidine rather than as an ionophore and may disturb the organization of the lipoprotein membrane, which in turn inactivates the membranebound epidermal A