CD region swap in Globins modifies heme coordination

IGNACIO BORON, LUCIANA CAPECE, DIANA WETZLER, AXEL BIDON-CHANAL, JAVIER LUQUE, MARCELO MARTI, DARIO ESTRIN Y ALEJANDRO NADRA

Cordoba

Congreso; 2do Congreso Asociación Argentina de Bioinformática y Biología Computacional; 2011

Asociación Argentina de Bioinformática y Biología Computacional

Human Myoglobin (Mb) and hemoglobin are relevant examples of pentacoordinated (5c) heme proteins and many of their biological functions involve the coordination of exogenous ligands in the sixth position of the heme group. On the other hand, in several globins direct coordination of HisE7 to the Fe atom leads to the formation of a hexacoordinated (6c) globin, as noted in neuroglobin (Ngb) and cytoglobin, among others. In the case of Ngb, which is expressed in vertebrates nervous system, has been the subject of many investigations in the last years, but its function is still unclear. In our previous work, we have studied by computer simulation the 5c↔6c transition in wild type Ngb, and analized the main differences between this protein and Mb, observing that the flexibility of the CD region is a key factor in the hexacoordination process. In this work, we apply a theorical­ experimental aproach to interchange CD regions of Mb and Ngb, forming two chimeric proteins. We have studied these chimeric proteins by means of molecular dynamics simulations, and calculated the free energy profiles for the 5c↔6c process. The results indicate that chimeric Mb is able to form the 6c adduct, similarly to wt Ngb. In chimeric Ngb, the reduction of the flexibility in the CD region results in a significant increase of the energy barrier for the 6c→5c transition, Finally, we produced both recombinant chimeric proteins to evaluate their coordination state and ligand binding properties by spectroscopic methods. Our prelimnary results suggest differences between quimeric and wild­type proteins in agreement with the theoretical predictions.