Ambler R P, Meyer T E, Kamen M D
Institute of Cell and Molecular Biology, University of Edinburgh, Scotland.
Arch Biochem Biophys. 1993 Oct;306(1):215-22. doi: 10.1006/abbi.1993.1503.
Rhodopila globiformis HiPIP has a redox potential (ca. 450 mV) that is 100 mV higher than any other known iron-sulfur protein. The amino acid sequence contains 57 residues and can be aligned with that of Thiobacillus ferrooxidans without any insertions or deletions and is 51% identical. Rp. globiformis HiPIP is also similar to that of Rhodocyclus tenuis, but six- and two-residue gaps must be postulated and there is only 37% identity. Most of the amino acid residues near the iron-sulfur cluster are similar in these two species based on inspection of the three-dimensional structure of Rc. tenuis HiPIP. The reason for the higher redox potential may be a more hydrophilic environment of the Rp. globiformis HiPIP iron-sulfur cluster due to the above two deletions and to substitution of Ser 32 for Gly. Rp. globiformis is unusual in that it has a cytochrome c2 in addition to the HiPIP, and it too has a very high redox potential. These results suggest that the cytochrome c2 and HiPIP may function interchangeably and that the species normally resides in a very high potential environment, although it is not known to grow aerobically in the dark.
球形红假单胞菌（Rhodopila globiformis）的高电位铁硫蛋白（HiPIP）具有约450 mV的氧化还原电位，比任何其他已知的铁硫蛋白高100 mV。其氨基酸序列包含57个残基，可与氧化亚铁硫杆菌（Thiobacillus ferrooxidans）的序列进行比对，无需插入或缺失，且一致性为51%。球形红假单胞菌HiPIP也与纤细红环菌（Rhodocyclus tenuis）的HiPIP相似，但必须假定存在6个和2个残基的缺口，且一致性仅为37%。基于对纤细红环菌HiPIP三维结构的检查，这两个物种中铁硫簇附近的大多数氨基酸残基相似。氧化还原电位较高的原因可能是由于上述两个缺失以及32位丝氨酸被甘氨酸取代，导致球形红假单胞菌HiPIP铁硫簇的环境更亲水。球形红假单胞菌的不同寻常之处在于，除了HiPIP外，它还有一种细胞色素c2，其氧化还原电位也非常高。这些结果表明，细胞色素c2和HiPIP可能具有互换功能，且该物种通常存在于高电位环境中，尽管尚不清楚它在黑暗中是否能有氧生长。
