Binding of the N-terminal 63 kDa portion of connectin/titin to alpha-actinin as revealed by the yeast two-hybrid system.

Connectin/titin is a 3000 kDa protein which links the myosin filament to the Z-line in vertebrate striated muscle sarcomeres. To search for the Z-line proteins to which connectin binds, the yeast two-hybrid system was applied using cDNA coding the N-terminal 63 kDa fragment of connectin. Two clones coding the C-terminal half region of alpha-actinin (amino acids, 343-897 and 446-897) were obtained. Enzyme-linked immunosorbent assay clearly demonstrated the interactions of alpha-actinin and the N-terminal 63 kDa fragment of connectin in vitro. Thus it is concluded that the N-terminal 63 kDa portion of connectin binds to alpha-actinin in the Z-line of myofibrillar sarcomeres.