Vermaas W F, Van Rensen J J
Biochim Biophys Acta. 1981 Jul;636(2):168-74. doi: 10.1016/0005-2728(81)90090-6.
In CO2-depleted chloroplasts electron transport between the Photosystem II electron acceptor Q and plastoquinone is largely suppressed. In the presence of a high concentration of sodium formate (greater than 10 mM), which probably binds to the bicarbonate site, addition of bicarbonate restores the ferricyanide Hill reaction only after incubation in the dark. With lower formate concentrations bicarbonate is able to restore electron transport in the light. The Hill reaction rate in CO2-depleted chloroplasts after bicarbonate addition, divided by the rate in CO2-depleted chloroplasts before bicarbonate addition, shows a sharp optimum at pH 6.5. Furthermore, the rate-limiting step in bicarbonate action is probably diffusion. The results are explained in terms of a hypothetical model: the bicarbonate-binding site is located at the outer side of the thylakoid membrane, but not directly accessible from the "bulk". To reach the site from the bulk, the molecule has to pass a channel with negatively charge groups on its side walls. In the light these groups are more negatively charged than in the dark. Therefore, the formate ion cannot exchange for bicarbonate in the light, and a dark period is necessary to enable exchange of formate for bicarbonate.
在二氧化碳匮乏的叶绿体中，光系统II电子受体Q与质体醌之间的电子传递受到很大抑制。在高浓度甲酸钠（大于10 mM）存在的情况下，甲酸钠可能与碳酸氢盐位点结合，添加碳酸氢盐后，只有在黑暗中孵育后才能恢复铁氰化物希尔反应。当甲酸钠浓度较低时，碳酸氢盐能够在光照下恢复电子传递。添加碳酸氢盐后，二氧化碳匮乏的叶绿体中的希尔反应速率除以添加碳酸氢盐前二氧化碳匮乏的叶绿体中的反应速率，在pH 6.5时呈现出明显的最佳值。此外，碳酸氢盐作用的限速步骤可能是扩散。结果用一个假设模型来解释：碳酸氢盐结合位点位于类囊体膜的外侧，但不能直接从“本体”进入。为了从本体到达该位点，分子必须通过一个侧壁带有负电荷基团的通道。在光照下，这些基团比在黑暗中带更多的负电荷。因此，甲酸盐离子在光照下不能与碳酸氢盐交换，需要一段黑暗时间才能使甲酸盐与碳酸氢盐进行交换。
