Structural Rearrangements Due to Ligand Binding and Haem Replacement in Myoglobin and Leghaemoglobins

Abstract

Structural rearrangements in sperm whale myoglobin and leghaemoglobins caused by changes in the spin or oxidation state of the iron as a consequence of ligand binding have been measured by difference spectroscopy in the ultraviolet. When compared with the high‐spin acetate complex, ligands which cause a transition to the low‐spin state also cause large perturbations of tyrosine(s) remote from the haem pocket in myoglobin but only minor perturbations of tryptophan(s) in leghaemoglobin. This may indicate a weaker coupling between events at the haem site and conformational changes in the protein in leghaemoglobins. The absorption spectra of various haem‐liganded forms of the two proteins as wel..