Use of membrane vesicles to estimate the numbers of system y+ and system L amino acid transporters in human erythrocytes

C. M. Tse, D. A. Fincham, J. C. Ellory, J. D. Young

Research output: Contribution to journalArticle


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 (104 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 ~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 (~300 copies/cell). Calculated turnover numbers for L-lysine transport by system y+ at 37 °C are 24 s(-l) for zero-trans influx and 150 s(-l) for equilibrium-exchange influx.

Original languageEnglish (US)
Pages (from-to)565-568
Number of pages4
JournalBiochemical Journal
Issue number2
StatePublished - Jan 1 1991


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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