CONICET | Buscador de Institutos y Recursos Humanos

Globins are well-known proteins that generally exhibit two histidine residues close to the iron, so it could be expected them to coordinate the heme. Nevertheless, typical globins such as myoglobin (Mb) and hemoglobin are pentacoordinated (5c) with only one His binidng to the iron. In the last decade, however, many hexacoordinated (6c) globins were discovered and several roles for hexacoordination in protein function were proposed. We are interested in neuroglobin (Ngb), which is expressed in the nervous system of vertebrates and whose function is still under debate.Our goal is to shed light on the key determinants for heme 6c⇆5c equilibrium that regulates globin reactivity. For this purpose we engineered Mb and Ngb by swapping their CD region with the goal of exchanging the 6c⇆5c equilibrium behavior. Further, a point mutant was designed to enhance coordination shift. Results Residue contact map and dynamic properties of parent proteins are generally transferred to the chimeras. Stopped flow, laser flash photolysis and autoxidation experiments support this behaviortransfer. Altogether, our results confirm a significant role of the CD region in the modulation of the 5c⇆6c equilibrium and consequently in globins fuction, but also suggest contributions of other protein regions.