Carmeli C, Lifshitz Y
Department of Biochemistry, Tel Aviv University, Israel.
J Bacteriol. 1989 Dec;171(12):6521-5. doi: 10.1128/jb.171.12.6521-6525.1989.
Cytoplasmic membrane vesicles isolated from the gram-negative photosynthetic bacterium Rhodobacter capsulatus catalyzed the transport of nucleotides. No transport occurred in the intact bacteria unless they were pretreated with EDTA. The transport rate was measured by incorporation of radioactive phosphate into externally added ADP or by incorporation of nonradioactive phosphate into added labeled ADP. The catalytic activities which utilized the added ADP were photosynthetic ATP synthesis, Pi-ADP exchange, and adenylate kinase. These activities were shown to occur on the cytoplasmic side of the internal membrane. The products were found in the outer medium. The rate of nucleotide transport across the membranes was comparable to the rate of photophosphorylation. These results indicated that nucleotides can be transported across the cytoplasmic membrane but not across the outer membrane of the native R. capsulatus cell. Therefore, by analogy to the mitochondrial ATP-ADP translocator, the exchange might function as an energy transfer system to the periplasm of these bacteria.
从革兰氏阴性光合细菌荚膜红细菌中分离出的细胞质膜囊泡催化核苷酸的运输。完整细菌中不会发生运输，除非用乙二胺四乙酸（EDTA）对其进行预处理。运输速率通过将放射性磷酸盐掺入外部添加的二磷酸腺苷（ADP）中或通过将非放射性磷酸盐掺入添加的标记ADP中来测量。利用添加的ADP的催化活性包括光合ATP合成、磷酸-ADP交换和腺苷酸激酶。这些活性显示发生在内膜的细胞质一侧。产物存在于外部介质中。核苷酸跨膜运输的速率与光合磷酸化的速率相当。这些结果表明，核苷酸可以跨细胞质膜运输，但不能跨天然荚膜红细菌细胞的外膜运输。因此，类似于线粒体ATP-ADP转位酶，这种交换可能作为一种能量转移系统作用于这些细菌的周质。
