The adaptive evolution of polar fishes: Structure, function and molecular phylogeny of hemoglobin

emperature affects all molecular processes and is the major determinant of habitat suitability. Whilst there is an increasing understanding of evolutionary adaptation to temperature in some processes, several key questions often remain open about the structure-function relationships associated with protein thermal adaptation. Proteins, such as hemoglobin, are highly sensitive to temperature and therefore, their structural and functional properties mirror the thermal conditions encountered by species during their evolutionary histories. The most stable thermal environments are aquatic; research on polar fishes has provided important insights into the details of thermal adaptation. In polar fishes, the evolution of hemoglobin includes adaptations with implications at the biochemical, physiological and structural levels. Although both are cold, the Northern and Southern polar oceans have very different oceanographic features. In comparison with Antarctic fish of the suborder Notothenioidei, Arctic fish are characterised by higher biodiversity and hemoglobin multiplicity. Within the study of the molecular bases of cold adaptation in fish inhabiting the polar habitats, and taking advantage of the information available on hemoglobin structure and function, the evolutionary history of the α and β globins of Arctic and Antarctic fish hemoglobins has been analysed, under the assumption of the molecular-clock hypothesis

EVOLUTION AND BIODIVERSITY IN THE ANTARCTIC - THE RESPONSE OF LIFE TO CHANGE (EBA): ROLE AND LEGACY

The international, multi- and cross-disciplinary programme Evolution and Biodiversity in the Antarctic: the Response of Life to Change (EBA), launched by the Scientific Committee for Antarctic Research (SCAR) in 2004, covers most of Antarctic biological research in the marine, terrestrial and freshwater realms, assembling almost one hundred teams. It liaises with physical, geological and historical disciplines, because of the intimate connection between the living and abiotic environments. Cross-linkages are being established with SCAR Programmes in other disciplines. The cooperative and cross-disciplinary research of EBA is a long-term legacy, in particular for evolutionary and biodiversity information. EBA has direct relevance to Global Change, because it addresses the impacts of the latter on biodiversity, evolutionary adaptations and community dynamics. It has been a Lead Project of the International Polar Year (IPY, 2007-9), envisaging links with the Arctic; the latter is undergoing rapid climate change, with progressive and fast decrease of sea and land ice. The responses of cold-adapted polar organisms provide information to analyse the effect of changes in general and foresee their impact at lower latitudes. EBA had been approved by SCAR until 2013; in 2009, the EBA community began planning its future. Cross-disciplinary science must be retained, but the EBA wide umbrella must be replaced by a more focussed approach. Antarctic research is expensive, and must be excellent, relevant, multi-national and well planned. The Peninsula and the sub-Antarctic islands are very important areas. The relationship between South America and Antarctica and their mutual influence must be considered. Climate change and its effects on biological systems and biodiversity in a changing environment are two major multi-disciplinary themes that may develop into new SCAR programmes. In the 2010 SCAR Meeting, the proposal of two distinct but complementary Science Programmes was brought to the attention of the Delegates, who agreed on further action along these lines.EVOLUCIÓN Y BIODIVERSIDAD EN LA ANTARTIDA: ESTUDIO DE LA RESPUESTA DE LOS SERES VIVOS AL CAMBIO (EBA); ROL Y LEGADO.  El programa internacional multi e inter disciplinario Evolución y Biodiversidad en la Antártida: Estudio de la Respuesta de los Seres Vivos al Cambio (EBA) lanzado por el Comité Cientíico de Investigación Antártica (SCAR) el año 2004, incluye gran parte de la investigación biológica Antártica de los ámbitos marino, terrestre y de agua dulce, reuniendo a un centenar de equipos de investigación. Este programa estuvo relacionado con disciplinas físicas, geológicas e históricas, debido  a  la  conexión  íntima  que  existe  entre  los  ambientes  vivos  y  abióticos.  Interrelaciones  están  siendo establecidas con los programas de SCAR en otras disciplinas. La investigación interdisciplinaria y cooperativa de EBA es un legado a largo plazo, en especial para la información evolutiva y de biodiversidad. EBA tiene una  relevancia  directa  en  el  Cambio  Global,  debido  a  que  trata  sobre  los  impactos  a  la  biodiversidad,  a  las adaptaciones evolutivas y a las dinámicas comunitarias. Ha sido un proyecto líder del Año Polar Internacional (IPY, 2007-09),  concibiendo vínculos con el Ártico. Esta zona está sometida a un rápido cambio climático con una disminución progresiva y rápida de hielo marino y terrestre. Las respuestas de los organismos polares adaptados al frío proveen de información para analizar el efecto de los cambios de manera general y aplicar este conocimiento para prever el impacto del cambio también a bajas latitudes. EBA fue aprobado por SCAR el año 2004 y se mantendrá activo hasta el año 2013. El año 2009, la comunidad EBA empezó a planiicar su futuro. La ciencia interdisciplinaria debe ser mantenida, pero el marco EBA debe ser reemplazado por una concepción mas focalizada. La investigación antártica es cara y debe ser excelente, relevante, multinacional y bien planiicada. La Península y las islas sub antárticas son áreas muy importantes y la relación entre Sudamérica y la Antártida y su mutua inluencia debe ser considerada. El cambio climático y sus efectos sobre los sistemas biológicos  y  la  biodiversidad  en  un  ambiente  cambiante,  son  los  dos  principales  temas  multidisciplinarios que  pueden  desarrollarse  dentro  de  los  nuevos  programas  SCAR.  En  la  reunión  de  SCAR  del  año  2010,  la propuesta de dos Programas Cientíicos distintos pero complementarios llamó la atención de los Delegados Nacionales que acordaron realizar acciones futuras de estas líneas de investigación.   Palabras clave: EBA; evolución adaptativa; diversidad biológica; cambio climático; ampliicación polar.EVOLUÇÃO E BIODIVERSIDADE NA ANTARTICA - A RESPOSTA DA VIDA À MUDANÇA (EBA): PAPEL E LEGADO. O programa interdisciplinar internacional Evolução e Biodiversidade na Antártica: a  Resposta  da Vida  à  Mudança  (EBA)  lançado  pelo  Comitê  Cientíico  para  Pesquisa Antártica  (SCAR)  em 2004 ampara a maioria das pesquisas biológicas nos ecossistemas Antárticos marinho, de água doce e terrestre, agregando quase uma centena de grupos de pesquisa. Devido a ligação íntima entre os ambientes bióticos e abióticos, o SCAR faz a união entre disciplinas físicas, geológicas e históricas. Ligações adicionais estão sendo estabelecidas com programas SCAR em outras disciplinas. A pesquisa cooperativa e interdisciplinar do EBA é um legado de longo prazo, principalmente com o que diz respeito a informação evolutiva e da biodiversidade. O EBA tem relevância direta com Mudança Global porque ele aborda os impactos das mudanças climáticas na biodiversidade, adaptação evolutiva e dinâmica de comunidades. O programa EBA tem sido um Projeto Líder do Ano Internacional Polar (IPY, 2007-9), ponderando uma ligação com o Ártico. Este está sofrendo rápida mudança climática com rápida e progressiva redução de gelo marinho e terrestre. As respostas de organismos polares adaptados ao frio fornece informações para a análise do efeito das mudanças em geral e para a previsão de impactos em latitudes menores. O EBA foi aprovado pelo SCAR em 2004 e deve durar até 2013. Em 2009, a comunidade do EBA começou a planejar seu futuro. A ciência interdisciplinar deve continuar, mas a grande cobertura do EBA deve ser substituída por uma abordagem mais focada. A pesquisa Antártica é dispendiosa e, portanto, deve ser de excelente qualidade, relevante, multinacional e bem planejada. A península Antártica e as ilhas subantárticas são áreas muito importantes e a relação entre a América do Sul e a Antártica e suas inluências mútuas devem ser consideradas. A mudança climática e seus efeitos em sistemas biológicos e na biodiversidade em um ambiente heterogêneo são dois principais temas interdisciplinares que podem se tornar novos programas SCAR. No encontro do SCAR em 2010, a proposta de dois Programas Cientíicos distintos, porém  complementares  foi  trazida  à  atenção  dos  Delegados  Nacionais,  que  por  sua  vez,  concordaram  com mais ações ao longo destas linhas de pesquisa. Palavras-chave: EBA; evolução adaptativa; biodiversidade; mudança climática; ampliicação polar

UV-protective compounds in marine organisms from the Southern Ocean

Solar radiation represents a key abiotic factor in the evolution of life in the oceans. In general, marine, biota particularly in euphotic and dysphotic zones depends directly or indirectly on light, but ultraviolet radiation (UV-R) can damage vital molecular machineries. UV-R induces the formation of reactive oxygen species (ROS) and impairs intracellular structures and enzymatic reactions. It can also affect organismal physiologies and eventually alter trophic chains at the ecosystem level. In Antarctica, physical drivers, such as sunlight, sea-ice, seasonality and low temperature are particularly influencing as compared to other regions. The springtime ozone depletion over the Southern Ocean makes organisms be more vulnerable to UV-R. Nonetheless, Antarctic species seem to possess analogous UV photoprotection and repair mechanisms as those found in organisms from other latitudes. The lack of data on species-specific responses towards increased UV-B still limits the understanding about the ecological impact and the tolerance levels related to ozone depletion in this region. The photobiology of Antarctic biota is largely unknown, in spite of representing a highly promising reservoir in the discovery of novel cosmeceutical products. This review compiles the most relevant information on photoprotection and UV-repair processes described in organisms from the Southern Ocean, in the context of this unique marine polar environment

Molecular adaptations in Antarctic fish and bacteria

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Hemoglobin is present as a canonical α2β2 tetramer in dopaminergic neurons

AbstractHemoglobin is the oxygen carrier in blood erythrocytes. Oxygen coordination is mediated by α2β2 tetrameric structure via binding of the ligand to the heme iron atom. This structure is essential for hemoglobin function in the blood. In the last few years, expression of hemoglobin has been found in atypical sites, including the brain. Transcripts for α and β chains of hemoglobin as well as hemoglobin immunoreactivity have been shown in mesencephalic A9 dopaminergic neurons, whose selective degeneration leads to Parkinson's disease. To gain further insights into the roles of hemoglobin in the brain, we examined its quaternary structure in dopaminergic neurons in vitro and in vivo. Our results indicate that (i) in mouse dopaminergic cell line stably over-expressing α and β chains, hemoglobin exists as an α2β2 tetramer; (ii) similarly to the over-expressed protein, endogenous hemoglobin forms a tetramer of 64kDa; (iii) hemoglobin also forms high molecular weight insoluble aggregates; and (iv) endogenous hemoglobin retains its tetrameric structure in mouse mesencephalon in vivo. In conclusion, these results suggest that neuronal hemoglobin may be endowed with some of the biochemical activities and biological function associated to its role in erythroid cells. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins

The Functionally Distinct Hemoglobins of the Arctic Spotted Wolffish Anarhichas minor

The Arctic fish Anarhichas minor, a benthic sedentary species, displays high hemoglobin multiplicity. The three major hemoglobins (Hb 1, Hb 2, and Hb 3) show important functional differences in pH and organophosphate regulation, subunit cooperativity, and response of oxygen binding to temperature. Hb 1 and Hb 2 display a low, effector-enhanced Bohr effect and no Root effect. In contrast, Hb 3 displays pronounced Bohr and Root effects, accompanied by strong organophosphate regulation. Hb 1 has the beta (beta(1)) chain in common with Hb 2; Hb 3 and Hb 2 share the alpha (alpha(2)) chain. The amino acid sequences have been established. Several substitutions in crucial positions were observed, such as Cys in place of C-terminal His in the beta(1) chain of Hb 1 and Hb 2. In Hb 3, Val E11 of the beta(2) chain is replaced by Ile. Homology modeling revealed an unusual structure of the Hb 3 binding site of inositol hexakisphoshate. Phylogenetic analysis indicated that only Hb 2 displays higher overall similarity with the major Antarctic hemoglobins. The oxygen transport system of A. minor differs remarkably from those of Antarctic Notothenioidei, indicating distinct evolutionary pathways in the regulatory mechanisms of the fish respiratory system in the two polar environments

The Evolution of Nitric Oxide Function: From Reactivity in the Prebiotic Earth to Examples of Biological Roles and Therapeutic Applications

Nitric oxide was once considered to be of marginal interest to the biological sciences and medicine; however, there is now wide recognition, but not yet a comprehensive understanding, of its functions and effects. NO is a reactive, toxic free radical with numerous biological targets, especially metal ions. However, NO and its reaction products also play key roles as reductant and oxidant in biological redox processes, in signal transduction, immunity and infection, as well as other roles. Consequently, it can be sensed, metabolized and modified in biological systems. Here, we present a brief overview of the chemistry and biology of NO—in particular, its origins in geological time and in contemporary biology, its toxic consequences and its critical biological functions. Given that NO, with its intrinsic reactivity, appeared in the early Earth’s atmosphere before the evolution of complex lifeforms, we speculate that the potential for toxicity preceded biological function. To examine this hypothesis, we consider the nature of non-biological and biological targets of NO, the evolution of biological mechanisms for NO detoxification, and how living organisms generate this multifunctional gas

Conformational Flexibility Drives Cold Adaptation in Pseudoalteromonas haloplanktis TAC125 Globins

Significance: Temperature is one of the most important drivers in shaping protein adaptations. Many biochemical and physiological processes are influenced by temperature. Proteins and enzymes from organisms living at low temperature are less stable in comparison to high-temperature adapted proteins. The lower stability is generally due to greater conformational flexibility. Recent Advances: Adaptive changes in the structure of cold-adapted proteins may occur at subunit interfaces, distant from the active site, thus producing energy changes associated with conformational transitions transmitted to the active site by allosteric modulation, valid also for monomeric proteins in which tertiary structural changes may play an essential role. Critical Issues: Despite efforts, the current experimental and computational methods still fail to produce general principles on protein evolution, since many changes are protein and species dependent. Environmental constraints or other biological cellular signals may override the ancestral information included in the structure of the protein, thus introducing inaccuracy in estimates and predictions on the evolutionary adaptations of proteins in response to cold adaptation. Future Directions: In this review, we describe the studies and approaches used to investigate stability and flexibility in the cold-adapted globins of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125. In fact, future research directions will be prescient on more detailed investigation of cold-adapted proteins and the role of fluctuations between different conformational states.Fil: Giordano, Daniela. Institute Of Biosciences And Bioresources; ItaliaFil: Boubeta, Fernando Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: di Prisco, Guido. Institute Of Biosciences And Bioresources; ItaliaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Smulevich, Giulietta. Firenze University; ItaliaFil: Viappiani, Christiano. Università di Parma; ItaliaFil: Verde, Cinzia. Institute Of Biosciences And Bioresources; Itali

Low affinity PEGylated hemoglobin from Trematomus bernacchii, a model for hemoglobin-based blood substitutes

<p>Abstract</p> <p>Background</p> <p>Conjugation of human and animal hemoglobins with polyethylene glycol has been widely explored as a means to develop blood substitutes, a novel pharmaceutical class to be used in surgery or emergency medicine. However, PEGylation of human hemoglobin led to products with significantly different oxygen binding properties with respect to the unmodified tetramer and high NO dioxygenase reactivity, known causes of toxicity. These recent findings call for the biotechnological development of stable, low-affinity PEGylated hemoglobins with low NO dioxygenase reactivity.</p> <p>Results</p> <p>To investigate the effects of PEGylation on protein structure and function, we compared the PEGylation products of human hemoglobin and <it>Trematomus bernacchii </it>hemoglobin, a natural variant endowed with a remarkably low oxygen affinity and high tetramer stability. We show that extension arm facilitated PEGylation chemistry based on the reaction of <it>T. bernacchii </it>hemoglobin with 2-iminothiolane and maleimido-functionalyzed polyethylene glycol (MW 5000 Da) leads to a tetraPEGylated product, more homogeneous than the corresponding derivative of human hemoglobin. PEGylated <it>T. bernacchii </it>hemoglobin largely retains the low affinity of the unmodified tetramer, with a p50 50 times higher than PEGylated human hemoglobin. Moreover, it is still sensitive to protons and the allosteric effector ATP, indicating the retention of allosteric regulation. It is also 10-fold less reactive towards nitrogen monoxide than PEGylated human hemoglobin.</p> <p>Conclusions</p> <p>These results indicate that PEGylated hemoglobins, provided that a suitable starting hemoglobin variant is chosen, can cover a wide range of oxygen-binding properties, potentially meeting the functional requirements of blood substitutes in terms of oxygen affinity, tetramer stability and NO dioxygenase reactivity.</p