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Myophilin of Echinococcus granulosus: isoforms and phosphorylation by protein kinase C

Published online by Cambridge University Press:  01 August 1997

R. M. MARTIN
Affiliation:
The University of Melbourne, Department of Veterinary Science, Werribee, Victoria 3030, Australia The Walter and Eliza Hall Institute of Medical Research, Post Office, Royal Melbourne Hospital Parkville, Victoria 3050, Australia
X. F. CSAR
Affiliation:
The Royal Melbourne Hospital, Department of Medicine, Parkville, Victoria 3052, Australia
R. B. GASSER
Affiliation:
The University of Melbourne, Department of Veterinary Science, Werribee, Victoria 3030, Australia
R. FELLEISEN
Affiliation:
University of Berne, Institute of Parasitology, Länggass-Strasse 122, CH-3012 Berne, Switzerland
M. W. LIGHTOWLERS
Affiliation:
The University of Melbourne, Department of Veterinary Science, Werribee, Victoria 3030, Australia

Abstract

Myophilin is a muscle-associated antigen of the taeniid cestode Echinococcus granulosus. This protein shows a high amino acid sequence homology with calponins and calponin-like proteins, which are proposed to be associated with the regulation of smooth muscle contraction. In order to provide supportive evidence for a relationship between these proteins, we characterized myophilin using electrophoretic, biochemical and molecular biological approaches. Two-dimensional protein electrophoretic separation of E. granulosus larval proteins defined 4 isoelectric isoforms of myophilin (α, β, γ and δ), which appeared to be a consequence of post-translational modification of a single gene product. It was also demonstrated biochemically that E. granulosus myophilin undergoes specific phosphorylation in vitro by protein kinase C (PKC). Finally, myophilin homologues were identified in extracts of Taenia hydatigena and T. ovis by immunoblot. A partial cDNA of the closely related species, E. multilocularis, was isolated by cloning procedures and showed 99% homology with the E. granulosus myophilin gene. The similarities of E. granulosus myophilin with calponins in their tissue localization, protein isoform patterns, ability to be phosphorylated in vitro by PKC, and the relatively conserved nature of the protein among related parasites suggest that myophilin may be associated with smooth muscle contraction.

Type
Research Article
Copyright
1997 Cambridge University Press

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