Over-expression of the β-carboxysomal CcmM protein in Synechococcus PCC7942 reveals a tight co-regulation of carboxysomal carbonic anhydrase (CcaA) and M58 content
Over-expression of the β-carboxysomal CcmM protein in Synechococcus PCC7942 reveals a tight co-regulation of carboxysomal carbonic anhydrase (CcaA) and M58 content
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DOI：
10.1007/s11120-011-9659-8
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发表时间：
2011-09-01
影响因子：
3.7
通讯作者：
Price, G. Dean
中科院分区：
文献类型：
--
作者：
Long, Benedict M.;Rae, Benjamin D.;Price, G. Dean
羧酸体，包含细胞的RuBisCO的补体，被一个特殊的蛋白质外壳包围，是蓝藻CO(2)浓缩机制的核心组成部分。两种形式的β -羧体蛋白CcmM （M58和M35）的比例可能影响羧体碳酸酐酶（CcaA）的含量。我们在β -蓝藻聚球菌PCC7942中过表达了M35和M58。过表达M58导致该蛋白在羧体中的数量显著增加，而M35的表达则减少，同时观察到羧体中CcaA的含量也随之增加。相反，M35过表达使羧小体M58含量降低，导致CcaA含量降低。与2% CO(2)培养的细胞相比，空气培养的野生型细胞羧基体的CcaA和M58含量略高，M35含量略低。在CcmM表达水平的范围内，M58与CcaA含量之间存在很强的相关性，表明羧基体M58: CcaA的化学计量是恒定的。这些结果也证实了M58在将CcaA招募到羧基小体中的作用，并表明需要严格调节M35和M58的翻译以产生具有适当CA含量的羧基小体。从上述过表达研究中得出的羧酸体蛋白比率分析表明，β -羧酸体蛋白化学计量学相对灵活。蛋白质绝对数量的测定支持了M35分布于整个β -羧基体的假设。提出了一种改进的β -羧基体填充模型。
Carboxysomes, containing the cell's complement of RuBisCO surrounded by a specialized protein shell, are a central component of the cyanobacterial CO(2)-concentrating mechanism. The ratio of two forms of the beta-carboxysomal protein CcmM (M58 and M35) may affect the carboxysomal carbonic anhydrase (CcaA) content. We have over-expressed both M35 and M58 in the beta-cyanobacterium Synechococcus PCC7942. Over-expression of M58 resulted in a marked increase in the amount of this protein in carboxysomes at the expense of M35, with a concomitant increase in the observed CcaA content of carboxysomes. Conversely, M35 over-expression diminished M58 content of carboxysomes and led to a decrease in CcaA content. Carboxysomes of air-grown wild-type cells contained slightly elevated CcaA and M58 content and slightly lower M35 content compared to their 2% CO(2)-grown counterparts. Over a range of CcmM expression levels, there was a strong correlation between M58 and CcaA content, indicating a constant carboxysomal M58: CcaA stoichiometry. These results also confirm a role for M58 in the recruitment of CcaA into the carboxysome and suggest a tight regulation of M35 and M58 translation is required to produce carboxysomes with an appropriate CA content. Analysis of carboxysomal protein ratios, resulting from the afore-mentioned over-expression studies, revealed that beta-carboxysomal protein stoichiometries are relatively flexible. Determination of absolute protein quantities supports the hypothesis that M35 is distributed throughout the beta-carboxysome. A modified beta-carboxysome packing model is presented.