Jc. Lambry et al., Molecular dynamics simulations of carbon monoxide dissociation from heme a(3) in cytochrome c oxidase from Paracoccus denitrificans, J PHYS CH A, 103(49), 1999, pp. 10132-10137
We have investigated ligand motions in the heme a(3)-CuB binuclear active s
ite of cytochrome c oxidase by molecular dynamics simulations. The starting
structural model is based on the two-subunit structure from the Paracoccus
denitrificans enzyme and contains carbon monoxide (CO) bound to heme a(3).
Short (1 ps) trajectories of the enzyme were calculated, each initiated by
the sudden breaking of the Fea(3)-CO bond. A comparison of two sets of cal
culations suggests a functional mechanistic role of the covalent bond betwe
en Tyr280 and His276, the latter being one of the three histidines coordina
ting the copper atom CuB. In particular, the presence of this bond enhances
the coupling of the CO motion to the environment and confines motion of CO
on the picosecond time scale to the region close to CuB. On the time scale
of a few hundred femtoseconds after dissociation, the most important movem
ent of CO consists of rotation over similar to 90 degrees and the most favo
rable position for binding to CuB appears to be occupied after 300-400 fs.
These results are discussed in the light of the recent suggestion that the
reaction coordinate of coherent reaction dynamics of heme a(3) after photod
issociation involves CO transfer to CuB (Liebl, U.; Lipowski, G.; Negrerie,
M.; Lambry J.-C.; Martin, J.-L.; Vos, M. H. Nature 1999, 401, 181.).