The Structures of Class II, Class III and Class IV Cytochromes c

Abstract

Judged spectrally, a wide variety of bacterial cytochromes c are known (Meyer & Kamen, 1982; Pettigrew & Moore, 1987: Chapter 3) but only a relatively small number are sufficiently characterised to be placed within the classification scheme described in section 1.3 of Pettigrew & Moore (1987). These are the class I cytochromes c, which are described in the previous chapter, and the class II and class III cytochromes c which are described in the present chapter. Photosynthetic reaction centre (PRC) cytochrome c from Rhodopseudomonas viridis is also described in the present chapter. This protein has only recently been characterised structurally, but it is clear that it does not fall into any of the currently defined classes (I, II or III) (Ambler, 1980). Accordingly, we have proposed that this protein be the prototype of a new group — class IV (Pettigrew & Moore, 1987: Table 1.4).