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

Eur J Biochem. 2001 Aug;268(16):4590-7. doi: 10.1046/j.1432-1327.2001.02386.x.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cytoskeletal Proteins / chemistry*
  • Cytoskeletal Proteins / metabolism
  • Dystroglycans
  • Epitopes
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / metabolism
  • Mice
  • Molecular Sequence Data
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism

Substances

  • Cytoskeletal Proteins
  • Epitopes
  • Membrane Glycoproteins
  • Recombinant Proteins
  • Dystroglycans

Grant support