Assembly of Transmembrane b-Type Cytochromes and Cytochrome Complexes

摘要: Cytochromes are involved in charge-transfer reactions, and many cytochromes contain a transmembrane domain part of membrane-localized electron transfer chains. Protoporphyrin IX (heme b) is the first heme product tetrapyrrole/heme biosynthesis pathway. In contrast to c-type cytochromes, there no need for specialized machinery catalyzing covalent attachment molecule b-type apo-cytochrome, nor cofactor further modified, as a-, d- o-type cytochromes. Thus, formation holo-cytochrome relatively simple this class proteins probably represents most ancient members However, assembly individual well larger cytochrome complexes involves multiple steps, which have be tightly controlled aligned: apo-protein needs synthesized, targeted to, integrated into membrane prior formation. Spontaneous folding polypeptide chain heme-binding cavity, allows specific tight binding cofactor. Additional biogenesis steps eventually required maturation complexes.