Download MendeleyNaturally Occurring A51V Variant of Human CytochromecDestabilizes the Native State and Enhances Peroxidase Activity.
Lei, H., Bowler, B.E.(2019) J Phys Chem B 123: 8939-8953
- PubMed: 31557440
- DOI: https://doi.org/10.1021/acs.jpcb.9b05869
- Primary Citation of Related Structures:
6DUJ - PubMed Abstract:
The A51V variant of human cytochrome c is linked to thrombocytopenia 4 (THC4), a condition that causes decreased blood platelet counts. A 1.82 Å structure of the A51V variant shows only minor changes in tertiary structure relative to the wild-type (WT) protein. Guanidine hydrochloride denaturation demonstrates that the global stability of the A51V variant is 1.3 kcal/mol less than that of the WT protein. The midpoint pH, pH 1/2 , of the alkaline transition of the A51V variant is 1 unit less than that of the WT protein. Stopped-flow pH jump experiments show that the A51V substitution affects the triggering ionization for one of two kinetically distinguishable alkaline conformers and enhances the accessibility of a high-spin heme transient. The pH 1/2 for acid unfolding of the A51V variant is 0.7 units higher than for that of the WT protein. Consistent with the greater accessibility of non-native conformers for the A51V variant, the k cat values for its peroxidase activity increase by 6- to 15-fold in the pH range of 5-8 versus those of the WT protein. These data along with previously reported data for the other THC4-linked variants, G41S and Y48H, underscore the role of Ω-loop C (residues 40-57) in modulating the peroxidase activity of cytochrome c early in apoptosis.
Organizational Affiliation:
Department of Chemistry and Biochemistry, Center for Bimolecular Structure and Dynamics , University of Montana , Missoula , Montana 59812 , United States.
