Refined purification and characterization of Z-protein

Using an improved procedure, Z-protein was prepared from myofibrils of chicken breast muscle. The yield of pure Z-protein increased to 10 mg per kg of muscle. The chain weight of Z-protein was 55,000 in the presence of SDS. However, Z-protein was eluted before aldolase (Mr 158,000) in Sephacryl S-400 column chromatography, and, therefore, it appeared to exist as a tetramer in a physiological salt solution. Z-protein had at least four isopeptides whose isoelectric points ranged from pH 6.0 to 6.4. Anti-Z-protein antiserum reacted equally with these isopeptides. The extinction coefficient of Z-protein at wavelength 278 nm was 4.2 (1%; light path, 1 cm). Z-protein which was purified according to this improved method did not bind to F-actin and alpha-actinin in a physiological salt solution.