We have used equilibrium values for L-leucine and L-lysine uptake by right-side-out vesicles to estimate the membrane abundance (sites/cell) of Na(+)-dependent amino acid transport systems L and y+ in human erythrocytes. All of the intravesicular space was accessible to L-leucine, as judged by comparisons with uridine uptake via the equilibrative nucleoside transporter (10(4) sites/cell). In contrast, only 28% of the total intravesicular space was accessible to L-lysine uptake via system y+. Since human erythrocyte membranes generate an average of approximately 1000 vesicles/cell, these data provide evidence that system L is a relatively high-abundance membrane transport protein in human erythrocytes, while system y+ is present in smaller amounts (approximately 300 copies/cell). Calculated turnover numbers for L-lysine transport by system y+ at 37 degrees C are 24 s-1 for zero-trans influx and 150 s-1 for equilibrium-exchange influx.
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Research Article|
July 15 1991
Use of membrane vesicles to estimate the numbers of system y+ and system L amino acid transporters in human erythrocytes
C M Tse;
C M Tse
1* Department of Medicine, G. I. Division, The Johns Hopkins University School of Medicine, 725 Wolfe Street, Hungterian # 503, Baltimore, MD 21205, U.S.A.
2†School of Applied Sciences, Wolverhampton Polytechnic, Wulfruna Street, Wolverhampton WVI ISB, U.K.
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D A Fincham;
D A Fincham
1* Department of Medicine, G. I. Division, The Johns Hopkins University School of Medicine, 725 Wolfe Street, Hungterian # 503, Baltimore, MD 21205, U.S.A.
5†School of Applied Sciences, Wolverhampton Polytechnic, Wulfruna Street, Wolverhampton WVI ISB, U.K.
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J C Ellory;
J C Ellory
1* Department of Medicine, G. I. Division, The Johns Hopkins University School of Medicine, 725 Wolfe Street, Hungterian # 503, Baltimore, MD 21205, U.S.A.
‡University Laboratory of Physiology, South Parks Road, Oxford OXl 3PT, U.K.
6†School of Applied Sciences, Wolverhampton Polytechnic, Wulfruna Street, Wolverhampton WVI ISB, U.K.
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J D Young
J D Young
§Department of Physiology, 7-55 Medical Sciences Building, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
7†School of Applied Sciences, Wolverhampton Polytechnic, Wulfruna Street, Wolverhampton WVI ISB, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1991 The Biochemical Society, London
1991
Biochem J (1991) 277 (2): 565–568.
Citation
C M Tse, D A Fincham, J C Ellory, J D Young; Use of membrane vesicles to estimate the numbers of system y+ and system L amino acid transporters in human erythrocytes. Biochem J 15 July 1991; 277 (2): 565–568. doi: https://doi.org/10.1042/bj2770565
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