类囊体膜的垛叠、松散与它的功能关系

菠菜完整叶绿体置于4mM MgCl_2或20 mM KCl低浓度介质中低渗10秒钟后,得到由Mg~(++)或K~+离子诱导的类囊体垛叠膜和松散膜。它们在功能上表现出明显的差异。垛叠膜有较高的毫秒级延迟光发射(ms-DLE),松散膜显著降低DLE的快相,垛叠膜比松散膜的9-AA荧光猝灭快,并保持稳定;而松散膜有H~+渗漏。在非循环或Fd催化的循环光合磷酸化中,垛叠膜比松散膜活力高。但是,若在同样的低渗介质中低渗1分钟以上,Mg~(++)离子诱导的垛叠膜,在显微结构上不同于低渗过10秒钟的垛叠膜,它垛叠较松,而且在磷酸化活力上也与松散膜差别不大。揭示了H~+传递速度受二个光系统、电子载体间的距离及偶联程度的限制。新鲜制备的垛叠或松散膜,在NADP~+还原系统中,具有相同的电子传递放O_2速度,说明电子传递速度在一定范围内不受膜间的距离和偶联程度的影响。但是松散膜不稳定,随着膜的老化而解联,牛血清白蛋白(BSA)能稳定松散膜的电子传递。

STACKING AND UNSTACKING OF THYLAKOID MEMBRANE AND ITS FUNCTIONS

The envelope of intact spinach chloroplast suspended in 4 mM MgCl_2 or 20 mM KCl can be broken. 4 mM Mg~(++) or 20 mM K~+ can induce grana to stack and unstack respectively. Their functions were different from each other. The millisecond delayed light emission (ms-DLE) in stacked membrane is stronger than unstacked membrane that decreases the fast phase ms-DLE, also it quenched 9-amino acridine (9-AA) fluorescence faster and remained stable, unstacked membrane decreased quenching of 9-AA fluorescence with time. In spite of non-cyclic or Fd-mediated cyclic photophosphorylation, the activity of stacked membrane was higher than that of unstacked.However, their activities were same if stacked and unstacked membranes were prepared by shocking for longer than 1 min, which revealed that proton transport rate was limited by the distance between two photosystems, the electron carriers, and degree of coupling of membrane compounds. The freshly stacked and unstacked membranes possessed the same electron transport rate in NADP~+ system. It suggested that electron transport was not affected by the distance, degree of coupling of membrane compounds, but unstacked membrane was unstable and uncoupled with aging. BSA could stablize its electron transport rate.