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Antarctic fish versus human cytoglobins – The same but yet so different

Research output: Contribution to journalArticle

Bert Cuypers, Stijn Vermeylen, Dietmar Hammerschmid, Stanislav Trashin, Vanoushe Rahemi, Albert Konijnenberg, Amy De Schutter, C.-h. Christina Cheng, Daniela Giordano, Cinzia Verde, Karolien De Wael, Frank Sobott, Sylvia Dewilde, Sabine Van Doorslaer

Original languageEnglish
Pages (from-to)66-78
JournalJournal of Inorganic Biochemistry
Volume173
Early online date28 Apr 2017
DOIs
Publication statusPublished - Aug 2017

King's Authors

Abstract

The cytoglobins of the Antarctic fish Chaenocephalus aceratus and Dissostichus mawsoni have many features in common with human cytoglobin. These cytoglobins are heme proteins in which the ferric and ferrous forms have a characteristic hexacoordination of the heme iron, i.e. axial ligation of two endogenous histidine residues, as confirmed by electron paramagnetic resonance, resonance Raman and optical absorption spectroscopy. The combined spectroscopic analysis revealed only small variations in the heme-pocket structure, in line with the small variations observed for the redox potential. Nevertheless, some striking differences were also discovered. Resonance Raman spectroscopy showed that the stabilization of an exogenous heme ligand, such as CO, occurs differently in human cytoglobin in comparison with Antarctic fish cytoglobins. Furthermore, while it has been extensively reported that human cytoglobin is essentially monomeric and can form an intramolecular disulfide bridge that can influence the ligand binding kinetics, 3D modeling of the Antarctic fish cytoglobins indicates that the cysteine residues are too far apart to form such an intramolecular bridge. Moreover, gel filtration and mass spectrometry reveal the occurrence of non-covalent multimers (up to pentamers) in the Antarctic fish cytoglobins that are formed at low concentrations. Stabilization of these oligomers by disulfide-bridge formation is possible, but not essential. If intermolecular disulfide bridges are formed, they influence the heme-pocket structure, as is shown by EPR measurements.

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