Samyn B, De Smet L, Van Driessche G, Meyer T E, Bartsch R G, Cusanovich M A, Van Beeumen J J
Department of Biochemistry, Physiology and Microbiology, University of Gent, Belgium.
Eur J Biochem. 1996 Mar 1;236(2):689-96. doi: 10.1111/j.1432-1033.1996.00689.x.
A minor cytochrome c-551 component of Chromatium vinosum was previously found to efficiently couple electron transfer between the cytochrome bc1 complex and the photosynthetic reaction center. We have now determined the amino acid sequence of this cytochrome c-551 and find that it is homologous to cytochrome c8 (formerly called Pseudomonas cytochrome c-551). It is most similar to Methylophilus methylotrophus, Rhodocyclus tenuis, and Azotobacter vinelandii cytochromes c8 (respectively, 57%, 52% and 51%). The C. vinosum cytochrome c8 has a single residue insertion relative to Pseudomonas and Azotobacter cytochromes c8. It has fewer charged residues than its homologs and is essentially neutral, which may explain why it is less soluble than the others. The cytochromes c8 are only very distantly related to the cytochromes c2 found in other species of purple bacteria which are much larger in size and which usually mediate electron transfer between the cytochrome bc1 complex and the reaction center. The photosynthetic pathway in Chromatium thus appears to be radically different from that in purple non-sulfur bacteria.
先前发现，嗜硫红假单胞菌（Chromatium vinosum）的一种次要细胞色素c-551成分能够有效地偶联细胞色素bc1复合物与光合反应中心之间的电子传递。我们现已确定了这种细胞色素c-551的氨基酸序列，并发现它与细胞色素c8（以前称为假单胞菌细胞色素c-551）同源。它与嗜甲基甲基ophilus甲基otrophus、红环菌（Rhodocyclus tenuis）和棕色固氮菌（Azotobacter vinelandii）的细胞色素c8最为相似（分别为57%、52%和51%）。相对于假单胞菌和棕色固氮菌的细胞色素c8，嗜硫红假单胞菌的细胞色素c8有一个单残基插入。它比其同源物的带电残基少，基本上呈中性，这可能解释了为什么它比其他细胞色素c8的溶解性差。细胞色素c8与在其他紫色细菌物种中发现的细胞色素c2的关系非常远，后者的尺寸要大得多，通常介导细胞色素bc1复合物与反应中心之间的电子传递。因此，嗜硫红假单胞菌中的光合途径似乎与紫色非硫细菌中的光合途径有根本不同。
