Mechanism of swelling activation of K-Cl cotransport in inside-out vesicles of LK sheep erythrocyte membranes

被引:17
作者
Kelley, SJ [1 ]
Dunham, PB [1 ]
机构
[1] SYRACUSE UNIV, DEPT BIOL, SYRACUSE, NY 13244 USA
来源
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY | 1996年 / 270卷 / 04期
关键词
volume regulation; red blood cells; secondary active transport; membrane vesicles;
D O I
10.1152/ajpcell.1996.270.4.C1122
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Stimulation by swelling of K-Cl cotransport was studied in inside-out vesicles (IOVs) made from membranes of LK sheep erythrocytes. The purpose was to understand this stimulation in terms of the three-state process proposed for regulation of the cotransporter (P. B. Dunham, J, Klimczak, and P. J. Logue. J. Gen. Physiol. 101: 733-765, 1993). The first step in this process, A --> B, is rate limiting and controlled by transphosphorylation reactions. The second step, B --> C, is fast; its control is unknown. Predictions were that maximum velocity (J(max)) of cotransport increases with A --> B and concentration at one-half J(max) (K-1/2) of K+ as a substrate decreases with B --> C. We tested the hypothesis that most transporters in IOVs are in the B state and that swelling activates cotransport in vesicles by the B --> C conversion. In accordance with this hypothesis, swelling should activate K+ influx with no discernible delay. It did. K-1/2 for K+ should decrease with swelling, and J(max) should not change. K-1/2 decreased 10-fold, and J(max) did not change. Inhibitors of transphosphorylation, reactions of A --> B, should not affect K+ flux into IOVs, and they did not. The results support the hypothesis: swelling activation of K+ flux into IOVs corresponds to B --> C. A mechanical change in the membrane causes a specific change in the cotransporter: an increase in apparent affinity for K+.
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页码:C1122 / C1130
页数:9
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