Omata T, Carlson T J, Ogawa T, Pierce J
Solar Energy Research Group, The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan.
Plant Physiol. 1990 May;93(1):305-11. doi: 10.1104/pp.93.1.305.
A 42-kilodalton cytoplasmic membrane protein is synthesized when high CO(2)-grown cells of Synechococcus PCC 7942 (Anacystis nidulans R2) are exposed to low CO(2). The structural gene for this protein (cmpA) has been cloned and sequenced and shown to encode a 450 amino acid polypeptide with a molecular mass of 49 kilodalton. A deletion mutant lacking the 42-kilodalton protein was obtained by transformation of Synechococcus PCC 7942 following in vitro mutagenesis of the cloned gene. There were no significant differences between the mutant and wild-type cells in their growth rates under either low or high CO(2) conditions. The activity of inorganic carbon (C(i)) transport in the mutant was as high as that in the wild-type strain. In both types of cells, CO(2) was the main species of C(i) transported and the activities of CO(2) and HCO(3) (-) transport increased when high CO(2)-grown cells were exposed to low CO(2). We conclude that the 42-kilodalton protein is not directly involved in the C(i)-accumulating mechanism of Synechococcus PCC 7942.
当聚球藻PCC 7942（巢状组囊藻R2）在高二氧化碳环境下生长的细胞暴露于低二氧化碳环境时，会合成一种42千道尔顿的细胞质膜蛋白。该蛋白的结构基因（cmpA）已被克隆和测序，结果显示其编码一个由450个氨基酸组成、分子量为49千道尔顿的多肽。通过对克隆基因进行体外诱变，然后转化聚球藻PCC 7942，获得了一个缺失42千道尔顿蛋白的缺失突变体。在低二氧化碳或高二氧化碳条件下，突变体细胞和野生型细胞的生长速率没有显著差异。突变体中无机碳（C(i)）转运活性与野生型菌株一样高。在这两种类型的细胞中，二氧化碳都是所转运的主要C(i)种类，并且当在高二氧化碳环境下生长的细胞暴露于低二氧化碳环境时，二氧化碳和碳酸氢根（HCO₃⁻）的转运活性都会增加。我们得出结论，42千道尔顿的蛋白不直接参与聚球藻PCC 7942的C(i)积累机制。
