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Journal of Molecular Evolution

, Volume 44 , Issue 3 , pp 242 –252 | Cite as

Experimental Indication in Favor of the Introns-Late Theory: The Receptor Tyrosine Kinase Gene from the Sponge Geodia cydonium

  • Vera  Gamulin
  • Alexander  Skorokhod
  • Vadim  Kavsan
  • Isabel M.  Müller
  • Werner E. G.  Müller

Abstract.

We have analyzed the gene that encodes receptor tyrosine kinase (RTK) from the marine sponge Geodia cydonium, which belongs to the most ancient and simple metazoan groups, the Porifera. RTKs are enzymes found only in metazoa. The sponge gene contains two introns in the extracellular part of the protein. However, the rest of the protein (transmembrane and intracellular part), including the tyrosine kinase (TK)-domain, is encoded by a single exon. In contrast, all TK genes, so far known only from higher animals (vertebrates), contain several introns especially in the TK-domain. The TK-domain of G. cydonium shows similarity with numerous members of receptor as well as nonreceptor TKs. Phylogenetic analysis of the sponge TK-domain indicates that this enzyme branched off first from the common tree of metazoan TK proteins. Consequently, we assume that introns, found in the TK-domains of genes from higher animals, were inserted into these genes after splitting off the sponge taxa from other metazoan organisms (over 600 million years ago). Our results support the view that ancient genes were not ``in pieces.''

Key words:Geodia cydonium— Sponge — Metazoan protein molecules 

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Copyright information

© Springer-Verlag New York Inc. 1997

Authors and Affiliations

  • Vera  Gamulin
    • 1
  • Alexander  Skorokhod
    • 2
  • Vadim  Kavsan
    • 2
  • Isabel M.  Müller
    • 3
  • Werner E. G.  Müller
    • 3
  1. 1.Department for Molecular Genetics, Institute Ruder Boskovic, 10000 Zagreb, CroatiaYU
  2. 2.Department of Biosynthesis of Nucleic Acids, Institute of Molecular Biology and Genetics, Ukrainian Academy of Sciences, 252627 Kiev, UkraineUA
  3. 3.Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099 Mainz, GermanyDE

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