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Identification of the beta-dystroglycan binding epitope within the C-terminal region of alpha-dystroglycan

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Author

  • Francesca Sciandra
  • Martina Schneider
  • Bruno Giardina
  • Stefan Baumgartner
  • Tamara C. Petrucci
  • Andrea Brancaccio

Summary, in English

Dystroglycan is a receptor for extracellular matrix proteins that plays a crucial role during embryogenesis in addition to adult tissue stabilization. A precursor product of a single gene is post-translationally cleaved to form two different subunits, alpha and beta. The extracellular alpha-dystroglycan is a membrane-associated, highly glycosylated protein that binds to various extracellular matrix molecules, whereas the transmembrane beta-dystroglycan binds, via its cytosolic domain, to dystrophin and many other proteins. alpha- and beta-Dystroglycan interact tightly but noncovalently. We have previously shown that the N-terminal region of beta-dystroglycan, beta-DG(654-750), binds to the C-terminal region of murine alpha-dystroglycan independently from glycosylation. Preparing a series of deleted recombinant fragments and using solid-phase binding assays, the C-terminal sequence of alpha-dystroglycan containing the binding epitope for beta-dystroglycan has been defined more precisely. We found that a region of 36 amino acids, from position 550-585, is required for binding the extracellular region, amino acids 654-750 of beta-dystroglycan. Recently, a dystroglycan-like gene was identified in Drosophila that showed a moderate degree of conservation with vertebrate dystroglycan (31% identity, 48% similarity). Surprisingly, the Drosophila sequence contains a region showing a higher degree of identity and conservation (45% and 66%) that coincides with the 550-585 sequence of vertebrate alpha-dystroglycan. We have expressed this Drosophila dystroglycan fragment and measured its binding to the extracellular region of vertebrate (murine) beta-dystroglycan (Kd = 6 +/- 1 microM). These data confirm the proper identification of the beta-dystroglycan binding epitope and stress the importance of this region during evolution. This finding might help the rational design of dystroglycan-specific binding drugs, that could have important biomedical applications.

Department/s

  • Invertebrate Developmental Biology, Stefan Baumgartner's group

Publishing year

2001

Language

English

Pages

4590-4597

Publication/Series

European Journal of Biochemistry

Volume

268

Issue

16

Document type

Journal article (letter)

Publisher

Wiley-Blackwell

Topic

  • Developmental Biology

Keywords

  • recombinant proteins
  • deletion mapping
  • protein–protein interaction
  • solid-phase binding assay
  • sequence alignment

Status

Published

Research group

  • Invertebrate Developmental Biology, Stefan Baumgartner's group

ISBN/ISSN/Other

  • ISSN: 0014-2956