Plant Physiol. Drug Metab Dispos
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Plant Physiology 70:1738-1742 (1982)
© 1982 American Society of Plant Biologists

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Articles

Characterization of In Vitro Proton Pumping by Microsomal Vesicles Isolated from Corn Coleoptiles 1

Irvin J. Mettler2, Suzanne Mandala and Lincoln Taiz3

Biology Department, University of California, Santa Cruz, Santa Cruz, California 95064, Thimann Laboratories, University of California, Santa Cruz, Santa Cruz, California 95064

Corn (Zea mays L. cv Golden Cross Bantam) coleoptile microsomal vesicles have been isolated which are capable of ATP-driven H+-transport as measured by [14C]methylamine accumulation and quinacrine fluorescence quenching. Formation of the pH gradient in vitro shows a high specificity for ATP·Mg, is temperature-sensitive, exhibits a pH optimum at 7.5, and is inhibited by carbonyl cyanide-m-chlorophenylhydrazone. Of the divalent cations tested, Mn2+ is almost as effective as Mg2+, while Ca2+ is ineffective. Excess divalent cations, particularly Ca2+, reduces the pH gradient. H+ transport is strongly promoted by anions, especially chloride, while potassium does not affect pump activity. Studies with 36Cl– indicate that ATP-driven H+ transport into the vesicles is associated with chloride uptake. Both carbonyl cyanide-m-chlorophenylhydrazone and the anion transport inhibitor, 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, inhibit methylamine accumulation and 36Cl– uptake. Proton pumping is also blocked by diethyl stilbestrol and N,N'-dicyclohexylcarbodiimide, but is insensitive to oligomycin and vanadate. These properties of the pump are inconsistent with either a mitochondrial or plasma membrane origin.

2 Present address: Stauffer Chemical Company, 1200 S. 47th Street, Richmond, CA 94804.

3 To whom reprint requests should be addressed.

1 Supported by grant PCM 77-25216 from the National Science Foundation.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1982 by the American Society of Plant Biologists