Marked Difference in the
Electronic Structure of Cyanide-Ligated Ferric Protoglobins
and Myoglobin Due to Heme Ruffling
- Publication date
- Publisher
Abstract
Electron paramagnetic resonance experiments reveal a
significant
difference between the principal <i>g</i> values (and hence
ligand-field parameters) of the ferric cyanide-ligated form of different
variants of the protoglobin of <i>Methanosarcina acetivorans</i> (<i>Ma</i>Pgb) and of horse heart myoglobin (hhMb). The
largest principal <i>g</i> value of the ferric cyanide-ligated <i>Ma</i>Pgb variants is found to be significantly lower than for
any of the other globins reported so far. This is at least partially
caused by the strong heme distortions as proven by the determination
of the hyperfine interaction of the heme nitrogens and mesoprotons.
Furthermore, the experiments confirm recent theoretical predictions
[Forti, F.; Boechi, L., Bikiel, D., Martí, M.A.; Nardini, M.;
Bolognesi, M.; Viappiani, C.; Estrin, D.; Luque, F. J. <i>J.
Phys. Chem</i>. <i>B</i> <b>2011</b>, <i>115</i>, 13771–13780] that Phe(G8)145 plays a crucial
role in the ligand modulation in <i>Ma</i>Pgb. Finally,
the influence of the N-terminal 20 amino-acid chain on the heme pocket
in these protoglobins is also proven