A new structural protein located in the Z lines of chicken skeletal muscle.

A new structural protein was purified from a prolonged 0.6 M KI extract of residues of chicken skeletal myofibrils, from which myosin, actin, and some other proteins had been removed. The protein had a chain weight of 55,000. The indirect immunofluorescence technique using antiserum against the 55,000 dalton protein revealed that the protein was exclusively located in the Z lines of a myofibril. The new protein formed lattice structures in vitro which were similar to those observed in the Z lines in situ.