Biophysical characterisation of neuroglobin of the icefish, a natural knockout for hemoglobin and myoglobin. Comparison with human neuroglobin.

• Published in: PLoS ONE
• Main Authors: Daniela Giordano, Ignacio Boron, Stefania Abbruzzetti, Wendy Van Leuven, Francesco P Nicoletti, Flavio Forti, Stefano Bruno, C-H Christina Cheng, Luc Moens, Guido di Prisco, Alejandro D Nadra, Darío Estrin, Giulietta Smulevich, Sylvia Dewilde, Cristiano Viappiani, Cinzia Verde
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2012
• Subjects: Medicine; R; Science; Q; Antarctic; The Antarctic; Antarc*; Icefish
• Online Access: https://doi.org/10.1371/journal.pone.0044508; https://doaj.org/article/b9f7268e7c4140a3b2f62ffbeed68267

The Antarctic icefish Chaenocephalus aceratus lacks the globins common to most vertebrates, hemoglobin and myoglobin, but has retained neuroglobin in the brain. This conserved globin has been cloned, over-expressed and purified. To highlight similarities and differences, the structural features of the neuroglobin of this colourless-blooded fish were compared with those of the well characterised human neuroglobin as well as with the neuroglobin from the retina of the red blooded, hemoglobin and myoglobin-containing, closely related Antarctic notothenioid Dissostichus mawsoni. A detailed structural and functional analysis of the two Antarctic fish neuroglobins was carried out by UV-visible and Resonance Raman spectroscopies, molecular dynamics simulations and laser-flash photolysis. Similar to the human protein, Antarctic fish neuroglobins can reversibly bind oxygen and CO in the Fe(2+) form, and show six-coordination by distal His in the absence of exogenous ligands. A very large and structured internal cavity, with discrete docking sites, was identified in the modelled three-dimensional structures of the Antarctic neuroglobins. Estimate of the free-energy barriers from laser-flash photolysis and Implicit Ligand Sampling showed that the cavities are accessible from the solvent in both proteins.Comparison of structural and functional properties suggests that the two Antarctic fish neuroglobins most likely preserved and possibly improved the function recently proposed for human neuroglobin in ligand multichemistry. Despite subtle differences, the adaptation of Antarctic fish neuroglobins does not seem to parallel the dramatic adaptation of the oxygen carrying globins, hemoglobin and myoglobin, in the same organisms.