Primary Citation of Related Structures: 4L6G, 4L77, 4LHT
PubMed Abstract:
In P450cin, Tyr81, Asp241, Asn242, two water molecules, and the substrate participate in a complex H-bonded network. The role of this H-bonded network in substrate binding and catalysis has been probed by crystallography, spectroscopy, kinetics, isothermal titration calorimetry (ITC), and molecular dynamics ...
In P450cin, Tyr81, Asp241, Asn242, two water molecules, and the substrate participate in a complex H-bonded network. The role of this H-bonded network in substrate binding and catalysis has been probed by crystallography, spectroscopy, kinetics, isothermal titration calorimetry (ITC), and molecular dynamics. For the Y81F mutant, the substrate binds about 20-fold more weakly and Vmax decreases by about 30% in comparison to WT. The enhanced susceptibility of the heme to H₂O₂-mediated destruction in Y81F suggests that this mutant favors the open, low-spin conformational state. Asn242 H-bonds directly with the substrate, and replacing this residue with Ala results in water taking the place of the missing Asn side chain. This mutant exhibits a 70% decrease in activity. Crystal structures and molecular dynamics simulations of substrate-bound complexes show that the solvent has more ready access to the active site, especially for the N242A mutant. This accounts for about a 64% uncoupling of electron transfer from substrate hydroxylation. These data indicate the importance of the interconnected water network on substrate binding and on the open/closed conformational equilibrium, which are both critically important for maintaining high-coupling efficiency.
Organizational Affiliation:
Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States.
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