Isolation of a-Connectin, an Elastic Protein, from Rabbit Skeletal

a-Connectin (also called titin 1) has been isolated from rabbit back muscle. Myofibrils were well washed with 5 mM NaHCO, and then extracted with 0.2 M sodium phosphate, pH 7.0. The extract was dialyzed against 0.1 M potassium phosphate, pH 7.0, to sediment myosin. The supernatant, adjusted to 0.18 M potassium phosphate, pH7.0, and 4M urea, was subjected to DEAE Toyopearl column chromatography. ^-Connectin was eluted in the flow-through fraction and a-connectin was eluted at around 0.1 M NaCl, when a 0 to 0.25 M NaCl gradient was applied. The separated a-connectin was dialyzed against 0.2 M potas-sium phosphate, pH 7.0. The resultant a-connectin showed the same mobility as that in an SDS extract of rabbit back muscle on SDS gel electrophoresis using 1.8 % polyacrylamide gels. A monoclonal antibody against chicken breast muscle /?-connectin reacted with the a-connectin isolated from rabbit back muscle. Connectin (also called titin) is a long, filamentous protein of vertebrate striated muscle (reviewed in Refs. 1 and 2). Connectin, with a MW as high as three million (3-5), links the myosin filament to the Z line (6, 7), and is responsibl