Deuterostomic Actin Genes and the Definition of the Chordates: cDNA Cloning and Gene Organization for Cephalochordates and Hemichordates |
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Authors: | Marc Bovenschulte Klaus Weber |
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Institution: | (1) Department of Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Goettingen, Germany, DE |
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Abstract: | The evolutionary relationship of muscle and nonmuscle actin isoforms in deuterostomia was studied by the isolation and characterization
of two actin genes from the cephalochordate Branchiostoma lanceolatum and two from the hemichordate Saccoglossus kowalevskii The Branchiostoma genes specify a muscle and a nonmuscle actin type, respectively. Together with earlier results on muscle actins from vertebrates
and urochordates, a N-terminal sequence signature is defined for chordate muscle actins. These diagnostic amino acid residues
separate the chordates from the echinoderms and other metazoa. Although the two Saccoglossus actins characterized so far lack the diagnostic residues, in line with the presumptive phylogenetic position of hemichordates
outside the chordates, a definitive conclusion can only be expected once the full complement of actin genes of Saccoglossus is established. Comparison of the intron patterns of the various deuterostomic actin genes shows that intron 330-3, which
is present in all vertebrate genes, is conspicuously absent from nonvertebrate genes. The possible origin of this intron is
discussed.
Received: 4 July 1997 / Accepted: 29 August 1997 |
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Keywords: | : Actin — Cephalochordates — Chordates — Cytoplasmic actin — Deuterostomes — Hemichordates — Introns — Muscle actins — Vertebrates |
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