Structure and function of hemoproteins from cold-adapted organism

• Main Author: Russo, Roberta
• Format: Doctoral or Postdoctoral Thesis
• Language: Italian; English
• Published: 2011
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://www.fedoa.unina.it/8854/; http://www.fedoa.unina.it/8854/1/Roberta_Russo.pdf; https://doi.org/10.6092/UNINA/FEDOA/8854

Environmental oxygen availability certainly plays a key role in the evolution of polar marine life, as suggested by the physiological and biochemical strategies that the organisms have adopted to acquire, deliver and scavenge oxygen. The psychrophilic Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 gives the opportunity to explore the cellular strategies adopted in vivo by cold-adapted microorganisms to cope with cold and high oxygen concentration. Within vertebrates, the dominant suborder Notothenioidei of the Southern Ocean is one of the most interesting models to study the evolutionary biological responses to extreme environment. Hemoproteins of cold-adapted organisms are likely to fulfil important physiological roles, not only in delivering oxygen to cells, but also in protecting them from the nitrosative and oxidative stress. This thesis will in particular focus on: (i) the structural and functional features of globins of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125, (ii) the role of neuroglobin (Ngb) recently identified in the brain of Antarctic notothenioid fish. The genome of the cold-adapted bacterium P. haloplanktis TAC125 contains multiple genes encoding three distinct monomeric hemoglobins (Hbs) exhibiting a 2/2 -helical fold (2/2Hb). One of these 2/2Hb (Ph-2/2HbO) has been over-expressed and characterised by spectroscopic analysis, kinetic measurements and computer simulation approaches (Howes et al., 2011; Giordano et al., 2011). The results indicate unique adaptive structural properties, that overall confer higher flexibility to the protein and may facilitate its functioning in the cold by providing greater freedom for the correct positioning of ligand(s). Similar to Ngb, the recombinant protein is hexacoordinated in the ferric and ferrous forms, and shows a strong dependence on pH (Howes et al., 2011; Giordano et al., 2011). Polar fish are a suitable model to learn more about the function of globins in the brain, and especially about their role in species devoid ...