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The comparative study on the solution structures of the oxidized bovine microsomal cytochrome b 5 and mutant V45H
Author(s) -
Zhang Qi,
Cao Chunyang,
Wang ZhiQiang,
Wang YunHua,
Wu Houming,
Huang ZhongXian
Publication year - 2004
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.04721104
Subject(s) - heme , chemistry , mutant , crystallography , hemeprotein , side chain , stereochemistry , cytochrome , imidazole , helix (gastropod) , biochemistry , biology , polymer , ecology , organic chemistry , snail , gene , enzyme
Abstract A comparative study on the solution structures of bovine microsomal cytochrome b 5 (T b 5 ) and the mutant V45H has been achieved by 1D and 2D 1 H‐NMR spectroscopy to clarify the differences in the solution conformations between these two proteins. The results reveal that the global folding of the V45H mutant in solution is unchanged, but the subtle changes exist in the orientation of the axial ligand His39, and heme vinyl groups. The side chain of His45 in V45H mutant extends to the outer edge of the heme pocket leaving a cavity at the site originally occupied by the inner methyl group of Val45 residue. In addition, the imidazole ring of axial ligand His39 rotates counterclockwise by ∼3° around the His‐Fe‐His axis, and the 4‐heme vinyl group turns to the space vacated by the removed side chain due to the mutation. Furthermore, the helix III of the heme pocket undergoes outward displacement, while the linkage between helix II and III is shifted leftward. These observations are not only consistent with the pattern of the pseudocontact shifts of the heme protons, but also well account for the lower stability of V45H mutant against heat and urea.