植物細胞における膜電位の発生機構と制御

元データ 日本膜学会

概要

Department of Botany, Faculty of Science, University of Tokyo, Hongo, Tokyo 113To study the electrogenic mechanism of the plant plasma membrane, intracellular chemical composition of <I>Chara australis</I>, a Characeae, was modified by the intracellular perfusion. It was suggested that the H<SUP>+</SUP>-extruding pump which is fueled by Mg·EATP is operating in the electrogenesis. Activity of the H<SUP>+</SUP>-pump was maximum at pH<SUB>o</SUB> 5.4-8.4 and at pHi 7. Light activates H<SUP>+</SUP>-pump and hyperpolarizes the membrane (light-induced potential change; LPC). Since LPC was not elicited in chloroplast-free <I>Spirogyra</I> cell which was prepared by cell-centrifugation, involvement of photosynthesis in LPC was concluded. Importance of electron transport in photosynthesis was suggested.<BR>There is another mechanism of electrogenesis in <I>Chara</I> cells. When internal ATP or Mg<SUP>2+</SUP> concentration was lowared greatly, the plasma membrane depolarized. When such a cell was stained with neutral red, a rapid light-induced potential change (rLPC) was observed. On illumination the membrane potential approached K<SUP>+</SUP>-equilibrium potential across th e plasma membrane and K<SUP>+</SUP>-channel inhibitors suppressed rLPC, evidence that rLPC is caused by activation of K<SUP>+</SUP>-channel. When the cell was made chloroplast-free by the centrifugation, rLPC was removed, and it was recovered by introducing spinach chloroplasts into the chloroplast-free <I>Chara</I> cell. Involvement of electron transport in rLPC was also suggested.

著者

新免 輝男 姫路工業大学・理・生命科学
新免 輝男 東京大学理学部植物学教室
田沢 仁 東京大学理学部植物学教室

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