Affiliations: Sackler Institute of Molecular Medicine, Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Note:  Address for correspondence: Sackler Institute of Molecular Medicine, Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel. Tel.: +972 3 640 9859; Fax: +972 3 640 5168; E-mail: [email protected]
Abstract: Infrared absorption spectra of carbon monoxide molecule coordinated by the heme iron of carbonmonoxy heme proteins are widely used to study their structure and dynamics. In this paper we use results of X-ray study of carbonmonoxy myoglobin to elucidate the structures of spectroscopically observed conformational substates of this protein. It is shown that A3 substate corresponds to the structure with water molecule hydrogen bonded to the distal histidine, whereas in the A1 conformation this molecule is absent. We also show that redistribution of electronic density of the distal histidine and the water molecule as a result of their interaction must be taken into account when predicting their positions in the heme pocket.
Keywords: Myoglobin, infrared, protein dynamics, conformational substates