BINDING OF THE N-TERMINAL 63 KDA PORTION OF CONNECTIN TITIN TO ALPHA-ACTININ AS REVEALED BY THE YEAST 2-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 sys tem was applied using cDNA coding the N-terminal 63 kDa fragment of co nnectin, Two clones coding the C-terminal half region of alpha-actinin (amino acids, 343-897 and 446-897) were obtained. Enzyme-linked immun osorbent assay clearly demonstrated the interactions of alpha-actinin and the N-terminal 63 kDa fragment of connectin in vitro, Thus it is c oncluded that the N-terminal 63 kDa portion of connectin binds to alph a-actinin in the Z-line of myofibrillar sarcomeres.