Wood P M
FEBS Lett. 1983 Dec 12;164(2):223-6. doi: 10.1016/0014-5793(83)80289-0.
The hypothesis presented is that the different classes of c-type cytochrome originated as proteins located in the bacterial periplasmic space, or on the periplasmic side of the cytoplasmic membrane. In these locations, covalent bonds between haem and protein prevented the haem from being lost to the surrounding medium. Subsequent evolution has led to internal location of c-type cytochromes in eucaryotes and cyanobacteria. The covalent links have been retained because of their structural role; a b-type cytochrome could be created with similar molecular properties, but its formation would require a large evolutionary jump. If this hypothesis is correct, it should be useful in unravelling electron transport chains with unconventional donors or acceptors. Apparent exceptions deserve further investigation.
所提出的假说是，不同类别的c型细胞色素最初是位于细菌周质空间或细胞质膜周质侧的蛋白质。在这些位置，血红素与蛋白质之间的共价键可防止血红素流失到周围介质中。随后的进化导致c型细胞色素在真核生物和蓝细菌中定位于内部。由于其结构作用，共价连接得以保留；可以创建具有相似分子特性的b型细胞色素，但其形成需要巨大的进化飞跃。如果这个假说正确，那么它将有助于阐明具有非常规供体或受体的电子传递链。明显的例外情况值得进一步研究。
