Kinetic analyses of mitochondrial 75Selenium uptake in Trigonella foenum-graecum seedlings exposed to selenium and mimosine

Uptake of (Se-75) added in vitro was followed in mitochondria isolated from Trigonella foenum-graecum seedlings grown under different Se status (0.5-1.0 ppm) and with added mimosine (0.1 mM). Uptake of Se-75 followed with added Na-2 (SeO3)-Se-75 upto 20 muM in the medium was nonlinear in all the groups. Kinetic analyses of the uptake of Se-75 for 1 min were carried out for all the groups. The results indicated a cooperative effect during Se transport. Graphical analyses using the Hill plot and Scatchard plot confirmed the existence of negative e cooperativity during Se-75 uptake. Scatchard plots were biphasic, suggesting the probable presence of two classes of binding Sites. The presence of succinate or ATP in the incubation medium inhibited Se-75 uptake by 40%. Studies with mitochondrial respiratory inhibitors indicated the uptake to be energy independent. A decrease in the uptake of Se-75 by 40% effected by HgCl2, N-ethyl maleimide, and iodoacetate confirmed the interaction of active thiols in the process. The present study confirms the controlled nature of Se-75 uptake by plant mitochondria.