Structure and sequence of the multihaem cytochrome c3.

The molecular structure of cytochrome c3 isolated from Desulfovibrio desulfuricans has been solved on the basis of its crystallographic determination at 2.5 A resolution and of an essentially complete sequence. The molecule consists of a single polypeptide chain wrapped around a very compact core of four non-parallel haems which present a relatively high degree of exposure to the solvent. Alignment of the amino acid sequences of cytochrome c3 from several species suggests that the structure reported here is characteristic of the cytochrome c3 group.