Heme is not required for Aquifex aeolicus cytochrome c(555) polypeptide folding.
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.
Yamanaka
Masaru
M
Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
Mita
Hajime
H
Yamamoto
Yasuhiko
Y
Sambongi
Yoshihiro
Y
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
D003580:Cytochromes; D010455:Peptides; D006418:Heme