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Functional diversification of sea lamprey globins in evolution and development
Angela Fago1, Kim Rohlfing2, Elin E Petersen1
1Department of Bioscience, Aarhus University, Denmark.
Biochimica Et Biophysica Acta. Proteins and Proteomics
|November 21, 2017
Summary
Vertebrate globin evolution shows distinct O2 transport and storage proteins in jawless fish like the sea lamprey. These proteins evolved independently, with functional differences observed between developmental stages and tissues.
Area of Science:
- * Evolutionary biology
- * Molecular biology
- * Biochemistry
Background:
- * Agnathans (jawless vertebrates) possess a unique globin gene repertoire distinct from gnathostomes (jawed vertebrates).
- * The sea lamprey (Petromyzon marinus) has multiple hemoglobin, myoglobin, globin X, and cytoglobin genes, with non-orthologous hemoglobins and myoglobins compared to jawed vertebrates.
- * This suggests independent evolution of oxygen transport and storage proteins in vertebrates.
Purpose of the Study:
- * To investigate the functional divergence of globin types during vertebrate evolution and ontogenesis.
- * To characterize the oxygen binding, quaternary assembly, and enzymatic activities of sea lamprey globins.
- * To compare sea lamprey cytoglobin with its mammalian counterpart.
Main Methods:
- * Determination of oxygen binding equilibria.
- * Analysis of quaternary assembly through gel filtration and molecular modeling.
- * Assay of nitrite reductase enzymatic activities.
Main Results:
- * Significant functional differentiation among sea lamprey globin types (hemoglobin, myoglobin, cytoglobin) based on developmental stage and tissue expression.
- * Cytoglobin (Cygb) and embryonic/larval hemoglobin (aHb6) exhibit cooperative oxygen binding and high oxygen affinity, unlike adult hemoglobin (aHb5a).
- * Sea lamprey myoglobin (aMb1) shows high oxygen affinity and lacks cooperativity, consistent with its role in muscle oxygen storage. Cytoglobin and aMb1 possess nitrite reductase activity.
Conclusions:
- * Oxygen transport and storage proteins evolved convergently in vertebrates, with distinct functional specializations in agnathans.
- * Sea lamprey myoglobin functions as an oxygen storage protein, while cytoglobin and hemoglobins play roles in oxygen transport and potentially other functions.
- * Conserved structural and functional properties of cytoglobin suggest its ancient role in vertebrates, dating back approximately 500 million years.
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