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Articles

Respiration-independent Binding of SR²⁺ to Bean Mitochondria ¹

^a Department of Botany, The University of Texas at Austin, Austin, Texas 78712

Binding of Sr²⁺ to bean mitochondria (Phaseolus vulgaris) shows a dissociation constant of 25 x 10^–6 and results in 40 to 50 nmoles of Sr²⁺ bound per mg protein. The binding is partially inhibited by valinomycin plus K⁺, 2, 4-dinitrophenol, as well as ruthenium red at a level of the 120 nmoles per mg protein. These compounds also partially inhibit active uptake of Sr²⁺. Calcium and Mg²⁺ also partially inhibit binding in the same magnitude as previously reported for inhibition of transport. Phosphate which is required for divalent cation transport is without effect on the binding of Sr²⁺. The possible role of the observed binding sites in divalent cation transport is discussed.

¹ Supported by Biomedical Sciences Support Grant FR-07091-05 from the General Research Branch, Division of Research Resources, Bureau of Health Professions, Education and Manpower Training, National Institutes of Health, and United States Public Health Service Training Grant 5TIGM00789 of the Cell Research Institute, The University of Texas, Austin, Texas 78712.