π-π interactions in structural stability: Role in superoxide dismutases

Abstract

In the present work, the influences of π–π interactions in superoxide dismutase (SOD) active centers were analyzed. The majority of the aromatic residues are involved in π–π interactions. Predominant type of interacting pairs is His–His and His–Trp pairs. In addition to π–π interactions, π residues also form πnetworks in SOD proteins. The π–π interactions are most favorable at the pair distance range of 5–7 Å. We observed that most of the π–π interactions shows stabilization energies in the range −4.2 to −12.6 kJ mol-1 , while the metal assisted π–π interactions showed an energy in the range −83.7 to −334.7 kJ mol-1 . Most of the π–π interacting residues were evolutionary conserved and thus probably important in maintaining the structural stability of proteins through these interactions. A high percentage of these residues could be considered as stabilization centers, contributing to the net stability of SOD proteins.