Gomelsky Mark, Kaplan Samuel
Microbiology (Reading). 1995 Aug;141 ( Pt 8):1805-1819. doi: 10.1099/13500872-141-8-1805.
The photosynthetic bacterium Rhodobacter sphaeroides responds to the transition from aerobiosis to anaerobic photosynthesis by increasing the expression of the photosynthesis genes. Mutants have been isolated based on their inability, following such a transition, to increase transcription of the puc operon encoding the apoproteins of the light-harvesting complex II. Mutant D5, a representative of one mutant class, described here, although remaining photosynthetically competent, produced only low levels of the photosynthetic spectral complexes. Complementation analysis revealed that either the gene for the photosynthesis response regulator prrA or the gene encoding its cognate sensor kinase, prrB, was capable of rescuing this mutant. However, partial complementation of this mutant was achieved by placing in trans additional copies of other defined genes from the cosmid library of R. sphaeroides. We describe this effect in detail, attributable to the hupT gene, which has been proposed to encode a histidine-kinase for the hydrogen uptake system in Rhodobacter capsulatus. The effect of HupT on the expression of the photosynthesis genes was mediated through PrrA and independent of a functioning hydrogen uptake system. Thus, we raise the possibility that HupT can participate in phosphorylation of the heterologous response regulator PrrA by so-called cross-talk and therefore partially compensate for the defect in the mutant described. The observation of cross-talk, together with the complementation analysis, allowed us to assign the original mutation to the prrB gene; this was confirmed by DNA sequencing. Analysis of cross-talk in the wild-type, prrB and prrA genetic backgrounds suggested that besides kinase activity, PrrB may possess phosphatase activity toward PrrA. We also report the cloning, organization and structure of some of the hup genes from R. sphaeroides and construction of a Hup- strain.
光合细菌球形红杆菌通过增加光合作用基因的表达来响应从需氧状态到厌氧光合作用的转变。基于在这种转变后无法增加编码光捕获复合体II脱辅基蛋白的puc操纵子的转录，已分离出突变体。这里描述的突变体D5是一个突变类别的代表，尽管它仍具有光合能力，但仅产生低水平的光合光谱复合体。互补分析表明，光合作用响应调节因子prrA基因或编码其同源传感激酶prrB的基因都能够拯救这个突变体。然而，通过从球形红杆菌的黏粒文库中转导入其他特定基因的额外拷贝，实现了对该突变体的部分互补。我们详细描述了这种效应，它归因于hupT基因，该基因被认为编码荚膜红细菌氢摄取系统的组氨酸激酶。HupT对光合作用基因表达的影响是通过PrrA介导的，并且独立于一个正常运作的氢摄取系统。因此，我们提出一种可能性，即HupT可以通过所谓的串扰参与异源响应调节因子PrrA的磷酸化，从而部分补偿所描述突变体中的缺陷。串扰的观察结果与互补分析一起，使我们将原始突变定位到prrB基因；这通过DNA测序得到了证实。在野生型、prrB和prrA遗传背景下对串扰的分析表明，除了激酶活性外，PrrB可能对PrrA具有磷酸酶活性。我们还报告了来自球形红杆菌的一些hup基因的克隆、组织和结构以及一个Hup-菌株的构建。
