Globin E is a myoglobin-related, respiratory protein highly expressed in lungfish oocytes

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  • Julia Lüdemann, Institute of Zoology, University of Hamburg, D-20146, Hamburg, Germany
  • Kellen Matos Verissimo, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, Brazil
  • Kimberley Dreger, Institute of Zoology, University of Hamburg, D-20146, Hamburg, Germany
  • Angela Fago
  • Igor Schneider, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, Brazil
  • Thorsten Burmester, Univ Hamburg, University of Hamburg, Inst Zool, Germany

Globins are a classical model system for the studies of protein evolution and function. Recent studies have shown that – besides the well-known haemoglobin and myoglobin – additional globin-types occur in vertebrates that serve different functions. Globin E (GbE) was originally identified as an eye-specific protein of birds that is distantly related to myoglobin. GbE is also present in turtles and the coelacanth but appeared to have been lost in other vertebrates. Here, we show that GbE additionally occurs in lungfish, the closest living relatives of the tetrapods. Each lungfish species harbours multiple (≥5) GbE gene copies. Surprisingly, GbE is exclusively and highly expressed in oocytes, with mRNA levels that exceed that of myoglobin in the heart. Thus, GbE is the first known oocyte-specific globin in vertebrates. No GbE transcripts were found in the ovary or egg transcriptomes of other vertebrates, suggesting a lungfish-specific function. Spectroscopic analysis and kinetic studies of recombinant GbE1 of the South American lungfish Lepidosiren paradoxa revealed a typical pentacoordinate globin with myoglobin-like O 2-binding kinetics, indicating similar functions. Our findings suggest that the multiple copies of GbE evolved to enhance O 2-supply in the developing embryo of lungfish, analogous to the embryonic and fetal haemoglobins of other vertebrates. In evolution, GbE must have changed its expression site from oocytes to eyes, or vice versa.

Original languageEnglish
Article number280
JournalScientific Reports
Volume9
Issue1
Number of pages11
ISSN2045-2322
DOIs
Publication statusPublished - Jan 2019

    Research areas

  • CYTOGLOBIN, EVOLUTION, FUNCTIONAL DIVERSIFICATION, GENE SUPERFAMILY, HEMOGLOBIN, HYPOXIA TOLERANCE, NEUROGLOBIN, NITRIC-OXIDE, PROVIDES INSIGHTS, REPERTOIRE

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