In Silico Insight into the Reductive Nitrosylation of Ferric Hemeproteins

Abstract

A combination of in silico methods was used to extend the 5 experimental description of the reductive nitrosylation mechanism in ferric 6 hemeproteins with the molecular details of the role of surrounding amino acids. 7 The computational strategy consisted in the estimation of potential energy 8 profiles for the transition process associated with the interactions of the 9 coordinated N(NO) moiety with O(H2O) or O(OH−) as nucleophiles, andwith distal amino acids as proton acceptors or affecting the stability of transitionstates. We inspected the reductive nitrosylation in three representativehemeproteins -sperm whale metmyoglobin, α subunit of human methemoglobinand nitrophorin 4 of Rhodnius prolixus. For each case, classical moleculardynamics simulations were performed in order to obtain relevant reactiveconformations, and a potential energy profile for the reactive step was obtainedusing adiabatic mapping or nudged elastic band approaches at the QM/MMlevel. Specifically, we report the role of a charged Arg45 of myoglobin in destabilizing the transition state when H2O acts as nucleophile, differently to the neutral Pro43 of the hemoglobin subunit. The case of the nitrophorin is unique in that the access of the required water molecules is scarce, thus, preventing the reaction.