Leghaemoglobin: a model for the investigation of haem protein axial ligation

The structural identity of the axial ligands is one of the major determinants of haem protein function and properties. In this work, the mobile distal histidine residue of soybean leghaemoglobin a has been replaced with a non-coordinating alanine residue (H61A variant) and the H61A variant has been characterised using a range of spectroscopic methods. These experiments provide a useful experimental framework for the examination of haem axial ligation and structure–function relationships.