INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The Peculiar Heme Pocket of the Truncated Hemoglobin of an antarctic bacterium
Autor/es:
LEONARDO BOECHI
Lugar:
St Simon Island - USA
Reunión:
Congreso; 50th Sanibel Symposium; 2010
Resumen:
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Truncated hemoglobins (trHbs) are heme
proteins present in bacteria, unicellular eukaryotes, and higher
plants. Three phylogenetic groups (N, O, and P) have been identified
in trHbs. We studied two truncated hemoglobin belonging to group O
and P, in order to explain some experimental results.
In the first case, the crystal
structure of truncated hemoglobin O of B. subtilis, does not show an
evident tunnel/cavity system connecting the protein active site with
the solvent, a fact that cannot be easily rationalized considering
the very high oxygen association rate. Moreover, resonant Raman
results of the CO bound protein, showed that a complex hydrogen bond
network exists in the distal cavity, making it difficult to assign
unambiguously the residues involved in the stabilization of the bound
ligand.
In the second case the truncated
hemoglobin P of C. jejuni shows three residues in the distal site
(His, Tyr, Trp) to stabilize the coordinated oxygen. Intriguingly
when one of them (His) is mutated by Leu, the O2 affinity is
increased.
For these reasons we performed
classical molecular dynamics simulations of the oxy, carboxy and
deoxy protein in both proteins in order to explain these experimental
results. We also performed Multiple Steered Molecular Dynamics to
compute the free energy profile for ligand migration, and a
classic-quantum approach (QM/MM) in order to compute the binding
between O2 and these proteins.