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Endogenous L-glutamate transport in oocytes of Xenopus laevis

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Steffgen,  Jürgen
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Koepsell,  Hermann
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Schwarz,  Wolfgang
Department of Cell Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Steffgen, J., Koepsell, H., & Schwarz, W. (1991). Endogenous L-glutamate transport in oocytes of Xenopus laevis. Biochimica et Biophysica Acta-Biomembranes, 1066(1), 14-20. doi:10.1016/0005-2736(91)90244-3.


Cite as: http://hdl.handle.net/21.11116/0000-0008-0521-D
Abstract
The existence of an endogenous Na+-glutamate cotransporter in the oocytes of Xenopus laevis is demonstrated. The transporter does not accept D-glutamate as substrate. The dependence on substrate displays two saturating components with low (K1/2 = 9 mM) and high (K1/2 = 0.35 microM) affinities for L-glutamate. The dependence on external Na+ exhibits a saturating component with a K1/2 value of about 5 mM and a component that has not saturated up to 110 mM Na+. In voltage-clamped oocytes, it is possible to demonstrate that Na+-dependent L-glutamate transport is directly coupled to countertransport of Rb+. The analysis of the voltage dependence of the Na+,K+-dependent L-glutamate uptake suggests that positive charges are moved inwardly during the transport cycle.