Role of heme distortion on the unusual oxygen affinity in protoglobin

FLAVIO FORTI; MARTINO BOLOGNESI; F. JAVIER LUQUE; MARCELO A. MARTÍ; DARÍO A. ESTRIN; DAMIÁN E. BIKIEL; LEONARDO BOECHI

San Andrés, Colombia

Congreso; QUITEL 2009, XXV Congress of theoretical chemistry of latin expression; 2009

Químicos Teóricos Expresión latina

A systematic study focused on the effect of the distortion of the porphyrin ring on the binding affinity forsmall ligands, especifically oxygen, is presented. Our results show that out-of-plane distortions decreasethe 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,strongly modulates the binding affinity. These findings shed light into the peculiar binding affinity ofMethanosarcina acetivorans protoglobin, a protein that contains a highly distorted heme. Overall, theresults highlight that in-plane distortions might by exploited by certain classes of hemeproteins to modulatethe ligand affinity.