Action of Protein Synthesis Inhibitors in Blocking Electrogenic H+ Efflux from Corn Roots

The block in the electrogenic H(+) efflux produced by protein synthesis inhibitors in corn root tissue can be released or by-passed by addition of fusicoccin or nigericin. The inhibition also lowers cell potential, and the release repolarizes. Associated with the inhibition of H(+) efflux is inhibition of K(+) influx and the growth of the root tip; fusicoccin partially relieves these inhibitions, but nigericin does not. The inhibition of H(+) efflux which arises from blocking the proton channel of the ATPase by oligomycin or N,N'-dicyclohexylcarbodiimide can also be partially relieved by fusicoccin, but not by nigericin; the inhibition produced by diethylstilbestrol is not relieved by fusicoccin.The results are discussed in terms of the presumed mode of action of fusicoccin on the plasmalemma ATPase. Inhibition of protein synthesis appears to inactivate the proton channel of the ATPase, possibly as the indirect result of disrupted metabolism. Fusicoccin reactivates or bypasses the blocked channel.