Biophysical Characterisation of Neuroglobin of the Icefish, a Natural Knockout for Hemoglobin and Myoglobin. Comparison with Human Neuroglobin

• Published in: PLoS ONE
• Main Authors: Giordano, Daniela, Boron, Ignacio, Abbruzzetti, Stefania, Van Leuven, Wendy, Nicoletti, Francesco P., Forti, Flavio, Bruno, Stefano, Cheng, C-H. Christina, Moens, Luc, di Prisco, Guido, Nadra, Alejandro D., Estrin, Darío, Smulevich, Giulietta, Dewilde, Sylvia, Viappiani, Cristiano, Verde, Cinzia
• Format: Text
• Language: English
• Published: Public Library of Science 2012
• Subjects: Research Article; Antarctic; The Antarctic; Antarc*; Icefish
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3513292; http://www.ncbi.nlm.nih.gov/pubmed/23226490; https://doi.org/10.1371/journal.pone.0044508

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 Fe2+ 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.