INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
artículos
Título:
Quaternary structure effects on the hexacoordination equilibrium in rice hemoglobin rHb1: Insights from molecular dynamics simulations
Autor/es:
MORZAN, U.; CAPECE, L.; MARTI, M.A.; ESTRIN, D.A.
Revista:
PROTEINS: STRUCTURE, FUNCTION AND GENETICS
Editorial:
WILEY-LISS, DIV JOHN WILEY & SONS INC
Referencias:
Lugar: New York; Año: 2013 vol. 81 p. 863 - 873
ISSN:
0887-3585
Resumen:
Nonsymbiotic hemoglobins (nsHbs) form a widely distributed class of
plant proteins, which function remains unknown. Despite the fact that
class 1 plant nonsymbiotic hemoglobins are hexacoordinate (6c) heme
proteins (hxHbs), their hexacoordination equilibrium constants are much
lower than in hxHbs from animals or bacteria. In addition, they are
characterized by having very high oxygen affinities and low oxygen
dissociation rate constants. Rice hemoglobin 1 (rHb1) is a class 1
nonsymbiotic hemoglobin. It crystallizes as a fully associated homodimer
with both subunits in 6c state, but showing slightly different
conformations, thus leading to an asymmetric crystallographic homodimer.
The residues that constitute the dimeric interface are conserved among
all nsHbs, suggesting that the quaternary structure could be relevant to
explain the chemical behavior and biological function of this family of
proteins. In this work, we analyze the molecular basis that determine
the hexacoordination equilibrium in rHb1. Our results indicate that
dynamical features of the quaternary structure significantly affect the
hexacoordination process. Specifically, we observe that the
pentacoordinate state is stabilized in the dimer with respect to the
isolated monomers. Moreover, the dimer behaves asymmetrically, in a
negative cooperative scheme. The results presented in this work are
fully consistent with our previous hypothesis about the key role played
by the nature of the CD region in determining the coordination state of
globins.