Cooperativity in Scapharca Dimeric Hemoglobin: Simulation of Binding Intermediates and Elucidation of the Role of Interfacial Water
| Citations: | 1 - 0 self |
BibTeX
@MISC{Zhou_cooperativityin,
author = {Yaoqi Zhou and Hongyi Zhou and Martin Karplus and Biophysique Isis Université},
title = {Cooperativity in Scapharca Dimeric Hemoglobin: Simulation of Binding Intermediates and Elucidation of the Role of Interfacial Water},
year = {}
}
Share
 |
 |
 |
 |
||
OpenURL
Abstract
Cooperative binding of ligands to proteins can serve to increase their efficiency and to regulate their activity. Thus, understanding of the mechanism of cooperativity is one of the central concerns of molecular biology. For the tetrameric human hemoglobin (HbA), the cooperative mechanism involves a reasonably well understood combination of tertiary and quaternary changes that occur during the binding process. The dimeric hemoglobin of Scapharca (HbI), which is composed of subunits with the same fold as in HbA, is also highly cooperative but the structural changes on ligand binding are small. A re-orientation of Phe97 in the binding pocket and changes in the number of interfacial water moleculess have been implicated in the cooperative mechanism. To explore the role of these factors, we have investigated models of partially liganded inter-mediate states of HbI with molecular dynamics simulation methods. Since, unlike HbA, no structures for intermediates are available, they were constructed by combining subunits from the unliganded and liganded dimers. Two structurally distinct intermediates were examined, and it was shown that the transition between the two intermediates is directly coupled to the number of interfacial water molecules. Further, it was found that there is a well-defined water channel that connects the interface between the subunits to bulk water. The bottleneck (gate) of the channel, which can be open or closed, is made of hydrophilic residues. The implication of the present results for the cooperative mechanism of HbI is discussed.
Keyphrases
scapharca dimeric hemoglobin interfacial water cooperative mechanism binding intermediate interfacial water molecule structural change binding process dimeric hemoglobin liganded dimer tetrameric human hemoglobin ligand binding quaternary change cooperative binding hydrophilic residue central concern molecular biology inter-mediate state well-defined water channel present result distinct intermediate binding pocket molecular dynamic simulation method understood combination
