O'Gara J P, Eraso J M, Kaplan S
Department of Microbiology and Molecular Genetics, The University of Texas Medical School, Houston, Texas 77030, USA.
J Bacteriol. 1998 Aug;180(16):4044-50. doi: 10.1128/JB.180.16.4044-4050.1998.
To further understand the proposed signal transduction pathway involving the presumed redox proteins RdxBH and cbb3 cytochrome oxidase in Rhodobacter sphaeroides 2.4.1, a series of mutants lacking components of both the Prr two-component activation system and the cbb3-type cytochrome oxidase or RdxBH were constructed. We report that under highly aerobic conditions, aberrant photosynthesis gene expression and spectral complex formation typical of cbb3- or RdxBH-deficient mutants were no longer observed when either prrA (encoding the response regulator of the Prr system) or prrB (encoding the presumed sensor kinase) was also deleted. These double-mutant strains are phenotypically identical to single-mutant PrrA and PrrB strains, suggesting that the signal(s) originating from the cbb3 terminal oxidase affects downstream puc and puf operon expression by acting exclusively through the Prr system. When the same double-mutant strains were examined under anaerobic dark dimethyl sulfoxide growth conditions, photosynthesis gene expression was obligatorily linked to the two-component activation system. However, photosynthesis gene expression under the same growth conditions was significantly higher in the cbb3 mutant strain when compared to that in the wild type. Similarly, under anaerobic photosynthetic conditions the high levels of the oxidized carotenoid, spheroidenone, which accumulate in cbb3-deficient mutants were nearly restored to normal in a PrrB- CcoP- double mutant. This observation, together with previously published results, suggests that the regulation of the CrtA-catalyzed reaction possesses both transcriptional and posttranscriptional regulatory effectors. We propose that the cbb3 cytochrome oxidase, which by definition can interact with external oxygen, serves to control the activity of the Prr two-component activation system under both aerobic and anaerobic conditions. Although independent from the cbb3 oxidase, the RdxBH proteins are also required for normal functioning of the Prr two-component activation system and are therefore believed to lie between the cbb3 oxidase in this oxygen-sensing, redox signaling pathway and the Prr activation system.
为了进一步了解球形红细菌2.4.1中涉及假定的氧化还原蛋白RdxBH和cbb3细胞色素氧化酶的信号转导途径，构建了一系列同时缺失Prr双组分激活系统以及cbb3型细胞色素氧化酶或RdxBH组分的突变体。我们报道，在高氧条件下，当prrA（编码Prr系统的应答调节子）或prrB（编码假定的传感激酶）也被缺失时，不再观察到cbb3或RdxBH缺陷型突变体典型的异常光合作用基因表达和光谱复合物形成。这些双突变菌株在表型上与单突变的PrrA和PrrB菌株相同，这表明源自cbb3末端氧化酶的信号仅通过Prr系统作用，从而影响下游puc和puf操纵子的表达。当在厌氧黑暗二甲基亚砜生长条件下检测相同的双突变菌株时，光合作用基因表达必然与双组分激活系统相关联。然而，在相同生长条件下，与野生型相比，cbb3突变菌株中的光合作用基因表达显著更高。同样，在厌氧光合条件下，在cbb3缺陷型突变体中积累的高水平氧化类胡萝卜素球形烯酮，在PrrB - CcoP双突变体中几乎恢复到正常水平。这一观察结果与先前发表的结果一起表明，CrtA催化反应的调节具有转录和转录后调节效应物。我们提出，根据定义可与外部氧气相互作用的cbb3细胞色素氧化酶，在有氧和无氧条件下均用于控制Prr双组分激活系统的活性。尽管RdxBH蛋白独立于cbb3氧化酶，但它们也是Prr双组分激活系统正常运作所必需的，因此被认为位于该氧传感、氧化还原信号通路中的cbb3氧化酶与Prr激活系统之间。
