The Greenland shark Somniosus microcephalus -Hemoglobins and ligand-binding properties

A large amount of data is currently available on the adaptive mechanisms of polar bony fish hemoglobins, but structural information on those of cartilaginous species is scarce. This study presents the first characterisation of the hemoglobin system of one of the longest-living vertebrate species (39...

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Bibliographic Details
Published in:PLOS ONE
Main Authors: Russo, Roberta, Giordano, Daniela, Paredi, Gianluca, Marchesani, Francesco, Milazzo, Lisa, Altomonte, Giovanna, Del Canale, Pietro, Abbruzzetti, Stefania, Ascenzi, Paolo, Di Prisco, Guido, Viappiani, Cristiano, Fago, Angela, Bruno, Stefano, Smulevich, Giulietta, Verde, Cinzia
Format: Article in Journal/Newspaper
Language:English
Published: 2017
Subjects:
RESONANCE RAMAN-SPECTRA
AMINO-ACID SEQUENCE
OXYGEN-BINDING
CARTILAGINOUS FISH
HETERODONTUS-PORTUSJACKSONI
ELASMOBRANCH HEMOGLOBIN
STRETCHING FREQUENCIES
MOLECULAR ADAPTATIONS
QUATERNARY STRUCTURES
NOTOTHENIOID FISHES
Arctic
Greenland
Somniosus microcephalus
Online Access:https://pure.au.dk/portal/da/publications/the-greenland-shark-somniosus-microcephalus-hemoglobins-and-ligandbinding-properties(be4e0b77-13b5-4880-9d04-a561caacb35d).html
https://doi.org/10.1371/journal.pone.0186181
https://pure.au.dk/ws/files/117859980/journal.pone.0186181.pdf
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Summary:A large amount of data is currently available on the adaptive mechanisms of polar bony fish hemoglobins, but structural information on those of cartilaginous species is scarce. This study presents the first characterisation of the hemoglobin system of one of the longest-living vertebrate species (392 +/- 120 years), the Arctic shark Somniosus microcephalus. Three major hemoglobins are found in its red blood cells and are made of two copies of the same a globin combined with two copies of three very similar beta subunits. The three hemoglobins show very similar oxygenation and carbonylation properties, which are unaffected by urea, a very important compound in marine elasmobranch physiology. They display identical electronic absorption and resonance Raman spectra, indicating that their heme-pocket structures are identical or highly similar. The quaternary transition equilibrium between the relaxed (R) and the tense (T) states is more dependent on physiological allosteric effectors than in human hemoglobin, as also demonstrated in polar teleost hemoglobins. Similar to other cartilaginous fishes, we found no evidence for functional differentiation among the three isoforms. The very similar ligand-binding properties suggest that regulatory control of O-2 transport may be at the cellular level and that it may involve changes in the cellular concentrations of allosteric effectors and/or variations of other systemic factors. The hemoglobins of this polar shark have evolved adaptive decreases in O2 affinity in comparison to temperate sharks.

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