Evolution of EF-hand calcium-modulated proteins. IV. Exon shuffling did not determine the domain compositions of EF-hand Proteins |
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Authors: | Robert H Kretsinger Susumu Nakayama |
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Institution: | (1) Department of Biology, University of Virginia, 22901 Charlottesville, VA, USA;(2) Present address: Department of Biochemistry, Nagasaki University School of Medicine, 12-4 Sakamoto-machi, 852 Nagasaki, Japan |
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Abstract: | Summary In the previous three reports in this series we demonstrated that the EF-hand family of proteins evolved by a complex pattern
of gene duplication, transposition, and splicing. The dendrograms based on exon sequences are nearly identical to those based
on protein sequences for troponin C, the essential light chain myosin, the regulatory light chain, and calpain. This validates
both the computational methods and the dendrograms for these subfamilies. The proposal of congruence for calmodulin, troponin,
C, essential light chain, and regulatory light chain was confirmed. There are, however, significant differences in the calmodulin
dendrograms computed from DNA and from protein sequences.
In this study we find that introns are distributed throughout the EF-hand domain and the interdomain regions. Further, dendrograms
based on intron type and distribution bear little resemblance to those based on protein or on DNA sequences. We conclude that
introns are inserted, and probably deleted, with relatively high frequency. Further, in the EF-hand family exons do not correspond
to structural domains and exon shuffling played little if any role in the evolution of this widely distributed homolog family.
Calmodulin has had a turbulent evolution. Its dendrograms based on protein sequence, exon sequence, 3′-tail sequence, intron
sequences, and intron positions all show significant differences. |
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Keywords: | EF-hand Calcium-binding protein Gene duplication Congruence Domain transposition Calmodulin Exon Intron Domain shuffling Parallel evolution |
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