In the photosynthetic bacteria, as in other N2-fixing bacteria, two main enzymes are involved in H2 metabolism: nitrogenase, which catalyses the photoproduction of H2, and a membrane-bound (NiFe) hydrogenase, which functions as an H2-uptake enzyme. The structural genes for Rhodobacter capsulatus and Rhodocyclus gelatinosus uptake hydrogenases were isolated and sequenced. They present the same organization, with the gene encoding the small subunit (hupS) (molecular masses 34.2 and 34.6 kDa, respectively) preceding the gene encoding the large one (hupL) (molecular masses 65.8 and 68.5 kDa, respectively). The two hupSL genes apparently belong to the same operon. The deduced protein sequences of the small and of the large subunits share nearly 80% and maximally 70% identity, respectively, with their counterparts in uptake hydrogenases found in N2-fixing bacteria. However, unlike in Bradyrhizobium japonicum, R. gelatinosus or Azotobacter chroococcum, another open reading frame (ORFX) was found downstream and contiguous to the R. capsulatus hupSL whose transcription seemed to depend on the same hup promoter as hupSL. ORFX contained 786 nucleotides capable of encoding a hydrophobic polypeptide of 262 amino acids (30.2 kDa).

中文翻译：

---

荚膜红细菌和明胶红细菌摄取氢化酶的分子生物学研究。

与其他固氮细菌一样，在光合细菌中，H2代谢涉及两种主要酶：催化H2光产生的固氮酶和充当H2吸收酶的膜结合（NiFe）加氢酶。分离了荚膜红球菌和明胶红球菌摄取氢化酶的结构基因并测序。他们提出了相同的组织，其编码小亚基（hupS）（分别为34.2和34.6 kDa的分子）的基因位于编码大亚基（hupL）（分别为65.8和68.5 kDa的分子）的基因之前。这两个hupSL基因显然属于同一操纵子。推导的小亚基和大亚基的蛋白质序列分别具有近80％和最大70％的同一性，与他们的同伴摄取固定在N2细菌中的氢化酶。但是，与日本根瘤菌（Bradyrhizobium japonicum），明胶罗非鱼（R. gelatinosus）或绿脓杆菌（Azotobacter chroococcum）不同，在荚膜罗非鱼hupSL的下游发现了另一个开放阅读框（ORFX），其转录似乎与hupSL依赖于相同的hup启动子。ORFX包含786个核苷酸，能够编码262个氨基酸（30.2 kDa）的疏水多肽。