Molecular model of hemoglobin N from Mycobacterium tuberculosis bound to lipid bilayers: a combined spectroscopic and computational study.

A singular aspect of the 2-on-2 hemoglobin structures of groups I and II is the presence of tunnels linking the protein surface to the distal heme pocket, supporting the storage and the diffusion of small apolar ligands to/from the buried active site. As the solubility of apolar ligands is greater in biological membranes than in solution, the association of these proteins with biological membranes may improve the efficiency of ligand capture. As very little is known on this subject, we have investigated the interactions between hemoglobin N (HbN), a group I 2-on-2 hemoglobin from the pathogenic Mycobacterium tuberculosis (Mtb), and biological membranes using both experimental techniques and MD simulations. HbN has a potent nitric oxide dioxygenase activity (HbN-Fe2+-O2 + •NO + H2O → HbN-Fe3+–OH2 + NO3–) that is thought to protect the aerobic respiration of Mtb from inhibition by •NO. Three different membrane compositions were chosen for the studies, representative of the mycobacterial plasma membrane and ...