Abstract
The transport specificity of system y+L of human erythrocytes was investigated and the carrier was found to accept a wide range of amino acids as substrates. Relative rates of entry for various amino acids were estimated from their trans-effects on the unidirectional efflux of l-[14C]-lysine. Some neutral amino acids, l-lysine and l-glutamic acid induced marked trans-acceleration of labeled lysine efflux; saturating concentrations of external l-leucine and l-lysine increased the rate by 5.3±0.63 and 6.2±0.54, respectively. The rate of translocation of the carrier-substrate complex is less dependent on the structure of the amino acid than binding. Translocation is slower for the bulkier analogues (l-tryptophan, l-phenylalanine); smaller amino acids, although weakly bound, are rapidly transported (l-alanine, l-serine). Half-saturation constants (±sem) calculated from this effect (l-lysine, 10.32±0.49 μm and l-leucine, 11.50±0.50 μm) agreed with those previously measured in cis-inhibition experiments. The degree of trans-acceleration caused by neutral amino acids did not differ significantly in Na+, Li+ or K+ medium, whereas the affinity for neutral amino acids was dramatically decreased if Na+ or Li+ were replaced by K+. The observation that specificity is principally expressed in substrate binding indicates that the carrier reorientation step is largely independent of the forces of interaction between the carrier and the transport site.
Similar content being viewed by others
References
Bertran, J., Magagnin, S., Werner, A., Markovich, D., Biber, J., Testar, X., Zorzano, A., Kühn, L., Palacín, M., Murer, H. 1992a. Stimulation of system y+-like amino acid transport by the heavy chain of human 4F2 surface antigen in Xenopus laevis oocytes. Proc. Natl. Acad. Sci. USA 89:5606–5610
Bertran, J., Werner, A., Chillaron, J., Nunes, V., Biber, J., Testar, X., Zorzano, A., Estivill, X., Murer, H., Palacín, M. 1993. Expression cloning of a human renal cDNA that induces high affinity transport of l-cystine shared with dibasic amino acids in Xenopus oocytes. J. Biol. Chem. 268:14842–14849
Bertran, J., Werner, A., Moore, M., Stange, G., Markovich, D., Biber, J., Testar, X., Zorzano, A., Palacín, M., Murer, H. 1992b. Expression cloning of a cDNA from rabbit kidney cortex that induces a single transport system for cystine and dibasic and neutral amino acids. Proc. Natl. Acad. Sci. USA 89:5601–5605
Cheeseman, C.I. 1983. Characteristics of lysine transport across the serosal pole of the anuran small intestine. J. Physiol. 338:87–97
Cheeseman, C.I. 1992. Role of intestinal basolateral membrane in absorption of nutrients. Am. J. Physiol. 263:R482-R488
Christensen, H.N., Antonioli, J.A. 1969. Cationic amino acid transport in the rabbit reticulocyte. Na+-dependent inhibition of Na+-independent transport. J. Biol. Chem. 244:1497–1504
Devés, R., Angelo, S., Chávez 1993. N-ethylmaleimide discriminates between two lysine transport systems in human erythrocytes. J. Physiol. 468:753–766
Devés, R., Chávez, P., Boyd, C.A.R. 1992. Identification of a new transport system(y+L) in human erythrocytes that recognizes lysine and leucine with high affinity. J. Physiol. 454:491–501
Devés, R., Krupka, R.M. 1978. A simple experimental approach to the determination of carrier transport parameters for unlabeled substrate analogs. Biochim. Biophys. Acta 556:524–532
Devés, R., Krupka, R.M. 1979. A general kinetic analysis of transport. Tests of the carrier model based on predicted relations among experimental parameters. Biochim. Biophys. Acta 556:533–547
Harvey, C.M., Muzyka, W.R., Yao, S.Y., Cheeseman, C.I., Young, J.D. 1993. Expression of rat intestinal l-lysine transport systems in isolated oocytes of Xenopus laevis. Am. J. Physiol. 265:G99-G106
Krupka, R.M. 1990. Expression of substrate specificity in facilitated transport systems. J. Membrane Biol. 117:69–78
Lee, W.S., Wells, R.G., Sabbag, R.V., Mohandas, T.K., Hediger, M.A. 1993. Cloning and chromosomal localization of a human kidney cDNA involved in cystine, dibasic, and neutral amino acid transport. J. Clin. Invest. 91:1959–1963
Mosckovitz, R., Ning, Y., Heimar, E., Felix, A., Tate, S.S., Udenfriend, S. Characterization of the rat neutral and basic amino acid transporter utilizing anti-peptide antibodies. Proc. Natl. Acad. Sci. USA 90:4022–4026
Munck, B.G., Schultz, S.G. 1969. Interactions between leucine and lysine transport in rabbit ileum. Biochim. Biophys. Acta 183:182–193
Rosenberg, R. 1981. l-Leucine transport in human red blood cells: A detailed kinetic analysis. J. Membrane Biol. 62:79–93
Toney, M.D., Hohenester, E., Cowan, S.W., Jansonius, J.N. 1993. Dialkylglycine decarboxylase structure: bifunctional active site and alkali metal sites. Science 261:756–759
Van Winkle, L.J., Campione, A.L., Gorman, J.M. 1988. Na+-independent transport of basic and zwitterionic amino acids in mouse blastocysts by a shared system and by processes which distinguish between these substrates. J. Biol. Chem. 263:3150–3163
Wells, R.G., Hediger, M. 1992. Cloning of a rat kidney cDNA that stimulates dibasic and neutral amino acid transport and has sequence similarity to glucosidases. Proc. Natl. Acad. Sci. USA 89: 5596–5600
Wells, R.G., Lee, W., Kanai, Y., Leiden, J.M., Hediger, M. 1992. The F42 antigen heavy chain induces uptake of neutral and dibasic amino acids in Xenopus oocytes. J. Biol. Chem. 267:15285–15288
Author information
Authors and Affiliations
Additional information
We wish to thank Dr C.A.R. Boyd for helpful discussions and Prof. H.N. Christensen for sharing with us very relevant bibliographic material. We are grateful to FONDECYT (1282/91) and DTI (B 2674) (Chile) for financial assistance.
Rights and permissions
About this article
Cite this article
Angelo, S., Devés, R. Amino acid transport system y+L of human erythrocytes: Specificity and cation dependence of the translocation step. J. Membarin Biol. 141, 183–192 (1994). https://doi.org/10.1007/BF00238252
Issue Date:
DOI: https://doi.org/10.1007/BF00238252