title: Heme is not required for Aquifex aeolicus cytochrome c(555) polypeptide folding.
abstract: In cytochrome c, it has been supposed that heme must bind to the apo polypeptide for structure formation. We constructed a C12A/C15A variant of hyperthermophilic Aquifex aeolicus cytochrome c(555) (AA c(555)) in which the covalently heme-binding Cys residues were replaced by Ala, and characterized its molecular features. The apo C12A/C15A variant had almost the same helical content as holo AA c(555), and spontaneously incorporated heme in vitro with no helical content change. These results suggest that the apo AA c(555) polypeptide is intrinsically structured without heme binding, this being the first case of a cytochrome c polypeptide. This finding provides a new suggestion as to cytochrome c formation, that heme is not necessarily required for cytochrome c polypeptide folding.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Yamanaka
authors.forename: Hajime
authors.initials: H
authors.lastname: Mita
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sambongi
mesh_terms: D001105:Archaea / Q000201:enzymology*; D002942:Circular Dichroism; D003580:Cytochromes / Q000737:chemistry / Q000378:metabolism*; D004795:Enzyme Stability; D006418:Heme / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003580:Cytochromes; D010455:Peptides; D006418:Heme