| Popis: |
Purified actin, prepared from both beef and rabbit myofibrils, on being subjected to electrophoresis on gels containing 7 m urea produced a diffuse, heterogeneous and lightly-staining band over a range of R m = 0·26 to 0·33. After protecting against oxidation by the addition of DTT (dithiothreitol), the actin band concentrated sharply at R m = 0·26 and exhibited little contamination. Tropomyosin prepared from both rabbit and beef muscle and chromatographed on DEAE-cellulose produced heterogeneous electrophoretic patterns with bands always being present at R m = 0·24 and 0·43. Treatment with DTT or sulphite prior to electrophoresis always produced a single band of R m = 0·43, which was concluded to be SH-reduced tropomyosin. Rabbit muscle troponin sulphydryl groups were not protected by DTT or sulphite, but evidence suggested that troponin was localised at R m = 0·88 upon electrophoresis. Both α-actinin and β-actinin were prepared from rabbit muscle. Each sedimented as a single symmetrical peak on ultracentrifugation. Upon urea-disc-gel-electrophoresis, α-actinin produced two bands at R m = 0·02 and 0·07 while β-actinin exhibited an inconsistent heterogeneous pattern. Extra protein prepared from rabbit myofibrils by washing 8–10 times and chromatographing on DEAE cellulose was eluted from the column into five fractions (I, I-A, II, III and IV) by increasing salt concentrations. Fractions I and IV were shown to be sarcoplasmic- and nucleo-proteins, respectively. Although fractions II and III were not identified, evidence suggests that they were not of myofibrillar origin. Fraction I-A appeared to be identical to troponin. Thus, results suggest that extra protein is an artifact of preparation. |
