Cytochrome complex essential for photosynthetic oxidation of both thiosulfate and sulfide in Rhodovulum sulfidophilum
Cytochrome complex essential for photosynthetic oxidation of both thiosulfate and sulfide in Rhodovulum sulfidophilum
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DOI：
10.1128/jb.183.20.6107-6118.2001
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发表时间：
2001-10-01
影响因子：
3.2
通讯作者：
Berks, BC
中科院分区：
文献类型：
--
作者：
Appia-Ayme, C;Little, PJ;Berks, BC
许多光合细菌利用无机硫化合物作为固定二氧化碳的电子供体。从具有光合作用的α -变形杆菌中纯化了硫代硫酸盐诱导的细胞色素c。细胞色素c（551）是二血红素30kda SoxA亚基和单血红素15kda SoxX亚基的异源二聚体。细胞色素c（551）结构基因是一个包含11个基因的sox位点的一部分。序列分析表明SoxX中血红素铁的配体是蛋氨酸和组氨酸，而这两种SoxA血红素预计都具有不寻常的半胱氨酸+组氨酸配位。soxA突变株不能在硫代硫酸盐或硫化物上光自养生长或氧化。因此，细胞色素c（551）对于这两种硫的代谢是必不可少的。野生型嗜硫杆菌的周质提取物表现出硫代硫酸盐：细胞色素c氧化还原酶活性。然而，只有在质周提取物中添加纯化的细胞色素c（551）时，才能测量soxA突变菌株的这种活性。在一种绿硫菌的基因组和系统发育不同的非光合自养生物中，可以发现与嗜硫杆菌sox位点相似的基因簇。
Many photosynthetic bacteria use inorganic sulfur compounds as electron donors for carbon dioxide fixation. A thiosulfate-induced cytochrome c has been purified from the photosynthetic alpha -proteobacterium Rhodovulum sulfidophilum. This cytochrome c(551) is a heterodimer of a diheme 30-kDa SoxA subunit and a monoheme 15-kDa SoxX subunit. The cytochrome c(551) structural genes are part of an 11-gene sox locus. Sequence analysis suggests that the ligands to the heme iron in SoxX are a methionine and a histidine, while both SoxA hemes are predicted to have unusual cysteine-plus-histidine coordination. A soxA mutant strain is unable to grow photoautotrophically on or oxidize either thiosulfate or sulfide. Cytochrome c(551) is thus essential for the metabolism of both these sulfur species. Periplasmic extracts of wild-type R. sulfidophilum exhibit thiosulfate: cytochrome c oxidoreductase activity. However, such activity can only be measured for a soxA mutant strain if the periplasmic extract is supplemented with purified cytochrome c(551). Gene clusters similar to the R. sulfidophilum sox locus can be found in the genome of a green sulfur bacterium and in phylogenetically diverse nonphotosynthetic autotrophs.