A novel method of extraction of TnC from skeletal muscle myofibrils

 Incubation of mechanically skinned barnacle myofibrillar bundles in 10 mM orthovanadate (pH 6.6) results in the loss of Ca²⁺-dependent force generation, which reduces to 0.98±0.006% (mean ±SEM, n=25) of control levels. Analysis of myofibrillar bundles by gel electrophoresis showed that tension loss is primarily due to the extraction of troponin C (TnC) (65.4±5.04% mean ±SEM, n=5). This is a novel finding, since treating cardiac fibres with orthovanadate results in the removal of both TnC and troponin I (TnI) (28). Ca²⁺ dependence was restored to the myofibrillar bundles following reconstitution with either native isoform of barnacle TnC (BTnC₁: 78.72±12.8%, n=9, BTnC₂: 82.73±20.3%, n=3). The reversible loss of Ca²⁺-dependent tension generation following the removal and replacement of TnC indicates that the regulation of contraction in the barnacle is controlled by thin-filament regulatory proteins. Received: 30 September 1998 / Accepted: 16 December 1998