The Fe-CO bond energy in myoglobin: a QM/MM study of the effect of tertiary structure.
The Fe-CO bond dissociation energy (BDE) in myoglobin (Mb) has been calculated with B3LYP quantum mechanics/molecular mechanics methods for 22 different Mb conformations, generated from molecular dynamics simulations. Our average BDE of 8.1 kcal/mol agrees well with experiment and shows that Mb weakens the Fe-CO bond by 5.8 kcal/mol; the calculations provide detailed atomistic insight into the origin of this effect. BDEs for Mb conformations with the R carbonmonoxy tertiary structure are on average 2.6 kcal/mol larger than those with the T deoxy tertiary structure, suggesting two functionally distinct allosteric states. This allostery is partly explained by the reduction in distal cavity steric crowding as Mb moves from its T to R tertiary structure.
Strickland
Nikki
N
Mulholland
Adrian J
AJ
Harvey
Jeremy N
JN
D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry*; D003198:Computer Simulation; D006418:Heme / Q000737:chemistry*; D006801:Humans; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry
D009211:Myoglobin; D006418:Heme; D002248:Carbon Monoxide; D007501:Iron; D010100:Oxygen