Direct binding of Torpedo syntrophin to dystrophin and the 87 kDa dystrophin homologue.

Syntrophin, a 58-kDa membrane-associated protein, is one component of a protein complex associated with dystrophin and other members of the dystrophin family, including the 87-kDa homologue (87K protein). To characterize interactions between synthrophin and 87K protein, we used an in vitro overlay binding assay. We demonstrate that purified Torpedo syntrophin binds directly to dystrophin and 87K. By expressing overlapping regions of the 87K protein as bacterial fusion proteins for binding targets, we show that a 52-amino acid region of 87K (residues 375-426) is sufficient for binding syntrophin.