Title
Unusual flexibility of distal and proximal histidine residues in the haem pocket of **Drosophila melanogaster** haemoglobin Unusual flexibility of distal and proximal histidine residues in the haem pocket of **Drosophila melanogaster** haemoglobin
Author
Faculty/Department
Faculty of Sciences. Physics
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences . Biomedical Sciences
Publication type
article
Publication
Cambridge ,
Subject
Physics
Source (journal)
Metallomics / Royal Society of Chemistry. - Cambridge
Volume/pages
1(2009) :3 , p. 256-264
ISSN
1756-5901
ISI
000269034300009
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Several pH-dependent low-spin ferric haem forms are identified in a frozen solution of the ferric 121CysSer mutant of Drosophila melanogaster haemoglobin (DmHb1*) using electron paramagnetic resonance (EPR) techniques. Different forms with EPR parameters typical of bis-histidine coordinated haem iron centers were observed. Strong pH-dependent changes in the EPR signatures were observed related to changes in the haem pocket. The pulsed EPR data indicate that both the distal and proximal histidine exhibit a large libration around the FeNHis axis. The resonance Raman spectra of the CO-ligated ferrous form of Drosophila melanogaster haemoglobin are typical of an open conformation, with little stabilization of the CO ligand by the surrounding amino-acid residues. The EPR data of the cyanide-ligated ferric DmHb1* indicates a close similarity with cyanide-ligated ferric myoglobin. The structural characteristics of DmHb1* are found to clearly differ from those of other bis-histidine-coordinated globins.
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