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Articles

Partial Characterization of Fusicoccin Binding to Receptor Sites on Oat Root Membranes ¹

Botany Department, University of Washington, Seattle, Washington 98195

The possibility that fusicoccin (FC) binds to plasma membrane-associated ATPases of oat (cv. Victory) roots has been examined. Specific FC-binding in vitro is localized primarily on plasma membrane-enriched fractions. This FC-binding is greatly reduced by pretreatment of the membrane vesicles at temperatures above 45 C or with trypsin, and the same treatments cause the release of already bound FC. These results support the idea that the FC receptor is a protein located on the plasma membrane.

Both active ATPases and FC-binding proteins were solubilized using 1% Triton X-100. When this material was fractionated using gel chromatography, the ATPase activity could be separated from the FC-binding proteins. The identity of the FC-binding proteins is discussed with regard to the extensive evidence which supports the involvement of plasma membrane-ATPase H⁺/K⁺ pumps in FC-stimulated acidification and K⁺ uptake.

¹ This work was supported by the Department of Energy Contract EY-76-S-06-2225 and National Science Foundation Grant (PCM) 78-22417 (to R. E. C.).