Characterization of the glutamate/aspartate-transport system in a symbiotic Nostoc sp.
The permeability properties of the cell membrane of a symbiotic Nostoc sp. for glutamate and aspartate were investigated. These compounds were translocated across the plasmalemma by a transport system which showed a very high affinity for glutamate and a lower one for aspartate. Since a concomitant release of glutamate was observed during the uptake of these two amino acids it is concluded that the transport proceeds via a counterexchange mechanism. In addition to this counterexchange a net release of glutamate occurred in the dark. Some aspects concerning the possible function of this transport system in the symbiotic association Geosiphon pyriforme are discussed.
Institut für Botanik II der Universität Salzburg, Lasserstrasse 39, A-5020, Salzburg, Austria.
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Strasser
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Falkner