Sulfhydyl group involvement in the modulation of neutral amino acid transport in thymocyte membrane vesicles

Abstract

Membrane vesicles from rat thymocytes accumulate 2-aminoisobutyric acid in the presence of 0. 1 M NaCl. Uptake is half maximal between 15 and 30 seconds after addition of the amino acid and reaches a plateau value after about 2 minutes. The uptake of 2-aminoisobutyric acid can be modulated by various sulfhydryl reagents. Reduced glutathione leads to an inhibition of uptake whereas oxidized glutathione increases uptake. Agents such as insulin and diamide which can induce disulfide formation lead to an activation of transport. These date indicate that uptake of the Na+-dependent amino acid, 2-aminoisobutyric acid, in thymocytes is modulated by a putative plasma membrane, sulfhydryl-containing protein.

The use of HgCl2 to evaluate the cosubstrate: Amino acid transport stoichiometry in ehrlich ascites tumor cells

“…Recent reports have demonstrated the inhibition of Na+-dependent amino acid transport in thymocyte vesicles by sulfhydryl reactive agents (Kwock, 1981). We have described a kinetic model for AIB transport in Ehrlich ascites tumor cells which suggests that Na+ (or H+) interacts with similar groups to stimulate the cotransport system (Smith and Robinson, 1981a).…”

“…Recent studies in Ehrlich tumor cells (Smith and Robinson, 1981a) and thymocyte vesicles (Kwock, 1981) have suggested the participation of sulfhydryl groups in Na+dependent amino acid transport. In the present study we have evaluated the use of HgC12 as an inhibitor of aaminoisobutyric acid (AIB) uptake in these cells.…”