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Updated: Feb 25, 2026
Measurement of Heme Synthesis Levels in Mammalian Cells
Published on: July 9, 2015
Characterization of Heme Orientational Disorder in a Myoglobin Reconstituted with a Trifluoromethyl-Group-Substituted
Yuki Kanai1, Ayaka Harada2, Tomokazu Shibata1
1Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.
Abstract:
The orientation of a CF3-substituted heme in sperm whale myoglobin and L29F, H64L, L29F/H64Q, and H64Q variant proteins has been investigated using 19F NMR spectroscopy to elucidate structural factors responsible for the thermodynamic stability of the heme orientational disorder, i.e., the presence of two heme orientations differing by a 180° rotation about the 5-15 meso axis, with respect to the protein moiety. Crystal structure of the met-aquo form of the wild-type myoglobin reconstituted with 13,17-bis(2-carboxylatoethyl)-3,8-diethyl-2,12,18-trimethyl-7-trifluoromethylporphyrinatoiron(III), determined at resolution of 1.25 Å, revealed the presence of the heme orientational disorder. Alterations of the salt bridge between the heme 13-propionate and Arg45(CD3) side chains due to the mutations resulted in equilibrium constants of the heme orientational disorder ranging between 0.42 and 1.4. Thus, the heme orientational disorder is affected by the salt bridge associated with the heme 13-propionate side chain, confirming the importance of the salt bridge in the heme binding to the protein.
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