This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (47) Citing Articles via Google Scholar Google Scholar Articles by Mandala, S. Articles by Taiz, L. Search for Related Content PubMed PubMed Citation Articles by Mandala, S. Articles by Taiz, L. Agricola Articles by Mandala, S. Articles by Taiz, L.

Articles

Localization of the Proton Pump of Corn Coleoptile Microsomal Membranes by Density Gradient Centrifugation ¹

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

Previous studies characterizing an ATP-dependent proton pump in microsomal membrane vesicles of corn coleoptiles led to the conclusion that the proton pump was neither mitochondrial nor plasma membrane in origin (Mettler, Mandala, Taiz 1982 Plant Physiol 70: 1738-1742). To facilitate positive identification of the vesicles, corn coleoptile microsomal membranes were fractionated on linear sucrose and dextran gradients, with ATP-dependent [¹⁴C]methylamine uptake as a probe for proton pumping. On sucrose gradients, proton pumping activity exhibited a density of 1.11 grams/cubic centimeter and was coincident with the endoplasmic reticulum (ER). In the presence of high magnesium, the ER shifted to a heavier density, while proton pumping activity showed no density shift. On linear dextran gradients, proton pumping activity peaked at a lighter density than the ER. The proton pump appears to be electrogenic since both [¹⁴C]SCN^– uptake and ³⁶Cl^– uptake activities coincided with [¹⁴C] methylamine uptake on dextran gradients. On the basis of density and transport properties, we conclude that the proton pumping vesicles are probably derived from the tonoplast. Nigericin-stimulated ATPase activity showed a broad distribution which did not coincide with any one membrane marker.

³ To whom reprint requests should be addressed.

¹ Supported by grant PCM77-25216 from the National Science Foundation.

This article has been cited by other articles:

				K. W. Beyenbach and H. Wieczorek The V-type H+ ATPase: molecular structure and function, physiological roles and regulation J. Exp. Biol., February 15, 2006; 209(4): 577 - 589. [Abstract] [Full Text] [PDF]