Hydrophobic regions bacterial cytochromes

The reaction between HiPIP and cytochrome c or bacterial cytochromes784 involves specific sites on both proteins, although no kinetic evidence for association was found. Reaction between Chr. vinosum and Rhodopseudomonas gelatinosa HiPIPs with modified cytochrome c (trinitro-phenyllysine-13)785 was more rapid than for the unmodified cytochrome c since modification of Lys-13 destabilizes the heme crevice, and because the hydrophobic TNP group facilitates electron transfer by interacting with a hydrophobic region of the HiPIP. 

The eight critical aromatic groups are not distributed at random over the molecule but tend to occur in pairs. Tyrosine-48 and phenylalanine-tyrosine-46 are found at the bottom of the heme crevice, where 48 helps to tie down the heme and 46 provides a continuation of the hydro-phobic patch formed by the edge of the heme. These residues are also present in identical positions in bacterial cytochromes Cj and C550. Phenylalanine-10 and tyrosine-phenylalanine-97 occur at the right of the molecule, in the midst of a region of packed hydrophobic side chains which has been called the right channel is important to remem-... 

Studies of the sequence changes in cytodirome c found in 30 species ranging from man through moth to castor bean show that the hydrophobic nature of the haem box is conserved. A number of residues on the left side including the aromatics Tyr-59,1 -67, and Tyr-74 are conserved, which is consistent with the importance of this part of the molecule to electron transfer. The character of the basic region is also conserved, which explains the observation that cytochrome c from one species will react in vitro with cytochrome-oxidase preparations from distantly related species. Modelbuilding studies on bacterial cytochromes show that the sequence of cytochrome C from Rhodospirillum rubrum with 114 amino-acids can be easily... 

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