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

Proton-linked subunit kinetic heterogeneity for carbon monoxide binding to hemoglobin from Chelidonichthys kumu

The pH dependence of CO binding kinetics to Chelidonichthys kumu hemoglobin (Hb) and human adult Hb has been investigated between pH 2.0 and 9.0 at 20 degrees C. For both Hbs, CO binding kinetics is characterized by two proton-linked transitions, with different pKa values for alpha- and beta-chains in C. kumu Hb, leading to a relevant functional kinetic heterogeneity at most pH values. On the other hand, in human adult Hb the CO binding does not display a functional heterogeneity. Lowering the pH from 9 to 6 brings about a decrease of the CO binding rate constants, to a different extent for human adult Hb and the two chains of C. kumu Hb. Further lowering the pH from 6 to 2 induces an enhancement of CO binding rate constants, probably related to the protonation of proximal HisF8 Nepsilon atom and the cleavage (or severe weakening) of the HisF8-Fe bond. The presence of physiological concentrations of ATP (approximately 3 mM) affects the pH dependence of CO binding kinetics to C. kumu. Moreover, the effect of temperature (between 8 degrees C and 38 degrees C) on CO binding kinetics has been investigated in the absence of ATP at different pH values. These results allow to interpret the functional kinetic heterogeneity of C. kumu Hb on the basis of different regulatory aspects in the alpha- and beta-subunits, as suggested by structural considerations

Molecular adaptations in Antarctic fish and bacteria

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The Unique Hemoglobin System of Pleuragramma antarcticum, an Antarctic Migratory Teleost STRUCTURE AND FUNCTION OF THE THREE COMPONENTS

Pleuragramma antarcticum (suborder Notothenioidei, family Nototheniidae) is the most abundant fish in the antarctic shelf. This pelagic species has a circum-antarctic distribution and is characterized by spawning migration. This species displays the highest multiplicity of major hemoglobins (three); the other notothenioids have a single one (except one species, having two) with relatively low oxygen affinity regulated by pH and organophosphates. The hemoglobins of P. antarcticum display strong Bohr and Root effects; however, they reveal important functional differences in subunit cooperativity and organophosphate regulation and, above all, in the response of oxygenation to temperature. Despite the substitution ValbetaE11 --> Ile found in Hb 2, which decreases the affinity in human mutants, the hemoglobins have similar oxygen affinity, higher than that of the other notothenioids. Hb 1 has the alpha chain in common with Hb 2 and the beta in common with Hb 3. The amino acid sequence of all four chains has been established. Thus the hematological features of P. antarcticum differ remarkably from those of antarctic notothenioids. This unique and sophisticated oxygen transport system may adequately meet the requirements of the unusual mode of life of this fish

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 Hemoglobins of the Antarctic Fishes Artedidraco orianae and Pogonophryne scotti AMINO ACID SEQUENCE, LACK OF COOPERATIVITY, AND LIGAND BINDING PROPERTIES

The oxygen-transport system of two species of Antarctic fishes belonging to the family Artedidraconidae,Artedidraco orianae and Pogonophryne scotti, was thoroughly investigated. The complete amino acid sequence of the α and β chains of the single hemoglobins of the two species was established. The oxygen-binding properties were also investigated, and were found not to differ significantly from those shown by blood, intact erythrocytes, and unstripped hemolysates. Both hemoglobins have unusually high oxygen affinity and display a relatively small Bohr effect; the Root effect is elicited only by organophosphates and is also reduced. Remarkably, the Hill coefficient is close to one in the whole pH range, indicating absence of cooperative oxygen binding which, in A. orianae hemoglobin, could be ascribed to the subunit heterogeneity shown upon oxygen dissociation. In comparison with the other families of the suborder Notothenioidei, the oxygen-transport system of these two species of Artedidraconidae has unique characteristics, which raise interesting questions on the mode of function of a multisubunit molecule and the relationship with cold adaptation

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

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