Role of heme distortion on oxygen affinity in heme proteins: the protoglobin case.

DAMIAN E BIKIEL; FLACIO FORTI; LEONARDO BOECHI; MARCO NARDINI; F. JAVIER LUQUE; MARCELO A MARTI; DARÍO A. ESTRIN

JOURNAL OF PHYSICAL CHEMISTRY B - (Print)

AMER CHEMICAL SOC

Año: 2010 p. 8536 - 8543

1520-6106

The chemical properties of heme proteins largely reflect the electronic properties of their heme group. Often, theporphyrin ring of the heme exhibits significant distortions from its isolated structure, but the impact of these distortionson the chemical properties of the heme is yet uncertain. A systematic study focused on the effects of the distortionof the macrocycle on the binding affinity for oxygen is presented. The results show that out-of-plane distortionsdecrease the binding affinity, while in-plane distortions can increase or decrease it. Among in-plane distortions,only the breathing mode, which involves the symmetric compression-expansion of the porphyrin ring, stronglymodulates the binding affinity. These findings shed light into the peculiar binding affinity of MethanosarcinaacetiVorans protoglobin, a protein that contains a highly distorted heme. Overall, the results highlight that in-planedistortions might be exploited by certain classes of heme proteins to modulate the ligand affinity.