J Integr Plant Biol. ›› 1996, Vol. 38 ›› Issue (9): -.

• Research Articles •    

Direct Measurement of the K+-Channel and Its Ion Selectivity in the Thylakoid Membrane from Spinach (Spinacea oleracea L.) Leaves

Li Le-gong, Yan Ji-qiong and Tang Zhang-cheng   

Abstract: Thylakoid vesicles were purified from spinach (Spinacea oleracea L. ) leaves by sucrose density gradient centrifugation and incorporated into planar lipid bilayers by stirring. At least one type of voltage-dependent K+ single-channel currents was found. Its conductance (between +60 mV and –60 mV ) was about 55 pS in symmetrical (cis: trans) 250 mmol/L KC1. This channel was sensitive to TEA (tetraethylammonium chloride) and the permeability ratio (PK+/PCl-) was about 14. 9. The selectivity of 55 pS channel determined from both reversal potentials under bi-ionic conditions or from conductance measurements in symmetrical solutions, was in the seguence of K+〉Na+〉Li+ 〉NH4+〉 Cs+. This potassium channel could act as involved in charge-balancing during light-driven proton uptake by thylakoid.

Key words: Thylakoid membrane, Ionic channel, Planar lipid bilayers, K+, Spinach

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