Conserved amphipathic helices near the N-terminus and C-terminus of the alpha subunit of cranin (dystroglycan)

Cranin (dystroglycan) is a ubiquitously expressed extracellular matrix rece ptor, synthesized as a single precursor, which is cleaved into an extracell ular subunit (alpha) and a transmembrane subunit (beta). The primary sequen ce of cranin (dystroglycan) is known from cDNA cloning, and the protein has been strongly implicated in morphogenesis, cell adhesion and human disease . Nevertheless, the domain structure of the alpha subunit has not been well studied; although the protein binds to matrix proteins, to the beta subuni t, to cell surfaces, and possibly to other membrane proteins such as sarcog lycans, the domains responsible for mediating these interactions remain unk nown. Here I report computer analyses that identify two distinctive amphipa thic alpha-helical regions near the N-terminus and C-terminus of the alpha subunit, which are conserved in all species for which sequence information is currently available. This finding should stimulate and guide experimenta l studies designed to understand how the alpha subunit is associated with t he cell surface and with its various ligands.