Tentoxin An uncompetitive inhibitor of lettuce chloroplast coupling factor 1 |
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Authors: | John A Steele Richard D Durbin Thomas F Uchytil Daniel H Rich |
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Institution: | 1. Plant Disease Resistance Research Unit, A.R.S., U.S.D.A., Department of Plant Pathology, Madison, Wisc. 53706, U.S.A.;2. School of Pharmacy, University of Wisconsin, Madison, Wisc. 53706, U.S.A. |
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Abstract: | The interaction of tentoxin with solubilized lettuce chloroplast coupling factor 1 was characterized by direct binding studies, measurement of the time course of ATPase inhibition, and steady-state enzyme kinetics. Neither substrates, products or Ca2+ competed with the tentoxin binding site, nor did they induce any large change in tentoxin affinity. The inhibition of lettuce chloroplast coupling factor 1 ATPase was found to be the time dependent, and at equilibrium the affinities estimated by equilibrium ultrafiltration and enzyme inhibition were similar (1.8 · 108M?1). The steady-state kinetics best fit an uncompetitive pattern suggesting that the inhibited steps follow an irreversible step occurring after ATP binding. |
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Keywords: | chloroplast coupling factor 1 |
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