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Increasing the conformational stability by replacement of heme axial ligand in c ‐type cytochrome
Author(s) -
Satoh Tadashi,
Itoga Akito,
Isogai Yasuhiro,
Kurihara Masaaki,
Yamada Seiji,
Natori Miwa,
Suzuki Noriko,
Suruga Kohei,
Kawachi Ryu,
Arahira Masaomi,
Nishio Toshiyuki,
Fukazawa Chikafusa,
Oku Tadatake
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)03615-3
Subject(s) - heme , chemistry , ligand (biochemistry) , cytochrome , mutant , wild type , cytochrome c , stereochemistry , steric effects , crystallography , hemeprotein , biochemistry , receptor , enzyme , mitochondrion , gene
To investigate the role of the heme axial ligand in the conformational stability of c ‐type cytochrome, we constructed M58C and M58H mutants of the red alga Porphyra yezoensis cytochrome c 6 in which the sixth heme iron ligand (Met58) was replaced with Cys and His residues, respectively. The Gibbs free energy change for unfolding of the M58H mutant in water (Δ G ° unf =1.48 kcal/mol) was lower than that of the wild‐type (2.43 kcal/mol), possibly due to the steric effects of the mutation on the apoprotein structure. On the other hand, the M58C mutant exhibited a Δ G ° unf of 5.45 kcal/mol, a significant increase by 3.02 kcal/mol compared with that of wild‐type. This increase was possibly responsible for the sixth heme axial bond of M58C mutant being more stable than that of wild‐type according to the heme‐bound denaturation curve. Based on these observations, we propose that the sixth heme axial ligand is an important key to determine the conformational stability of c ‐type cytochromes, and the sixth Cys heme ligand will give stabilizing effects.