化能自养细菌Calvin循环相关基因的组织和调节研究进展

Progress in Organization and Regulation of Calvin-Benson-Bassham Cycle Genes in Chemoautotrophic Bacteria

Calvin循环是化能自养细菌同化CO2的主要途径.该循环大多数酶由cbb基因编码.除保守的内在基因排列次序外,不同化能自养细菌cbb基因簇在基因大小和操纵子结构上存在差异.兼性化能自养菌cbb操纵子比专性化能自养菌受到更严格的调控,其调控作用主要由位于cbb操纵子上游编码LysR家族转录激活蛋白的cbbR基因执行.最近的研究表明,另外一些蛋白因子也可能参与cbb基因调控.尽管操纵子调控元件接收到的代谢信号仍是未知的,但一般认为细胞的氧化还原状态起着关键作用.推测cbb操纵子的表达调控整合于一个调控网络中.

CO2 fixation in the chemoautotrophic bacteria occurs via the Calvin-Benson-Bassham cycle, and most of the enzymes of the cycle are encoded by cbb genes. The cbb gene clusters of various bacteria are different in size and operon organization except the conservative internal gene arrangement. The cbb operons of facultative chemoautotrophic bacteria are regulated more strictly than those of obligate chemoautotrophic ones. And cbbR gene, which is typically located upstream of the regulated cbb operon, encodes a transcriptional activator of the LysR family and plays an important role in regulation of cbb genes. Additional regulatory proteins may also be involved. Although the metabolic signal received by the regulatory components of the operons is still unknown, the redox state of cell is believed to play a key role. It is supposed that the regulation of cbb operon expression is inteaTated into a regulatory network.