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Coupling of Protein Relaxation to Ligand Binding and Migration in Myoglobin

Summary: Coupling of Protein Relaxation to Ligand Binding and
Migration in Myoglobin
Noam Agmon
Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel
ABSTRACT Protein relaxation, ligand binding, and ligand migration into a hydrophobic cavity in myoglobin are unified by
a bounded diffusion model which produces an accurate fit to complex ligand rebinding data over eight decades in time and a 160
K temperature range, in qualitative agreement with time-resolved x-ray crystallography. Protein relaxation operates in a cyclic
manner to move the ligand away from the binding site.
Myoglobin (Mb), a small protein specialized for the binding
of small ligands, has been studied extensively as a model for
the possible coupling of ligand binding to ligand migration
and protein relaxation. Early measurements by Austin et al.
(1975), of CO rebinding to Mb after MbCO laser photolysis,
revealed complex nonexponential temporal behavior. It has
been interpreted as sequential ligand migration within the
A ) B # C # D # S; (1)
which slows down the recombination process at the longer
times. Here A is the bound Fe-CO state, in B the unbound


Source: Agmon, Noam - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry