Adenylate deaminase binding to synthetic thick filaments of myosin

Adenylate deaminase (AMP deaminase; AMP aminohydrolase, EC 3.5.4.6), a tetrameric enzyme found at particularly high concentrations in skeletal muscle, has previously been shown to bind strongly to the subfragment-2-portion of myosin in vitro and to the ends of the A band in vivo. It is shown here that when adenylate deaminase is dialyzed with skeletal myosin during formation of synthetic filaments at pH 7.0 it decorates the filament at 14.3-nm intervals, presumably in the region of exposed backbone between crossbridge levels. Optical diffraction of the aggregates reveals both enhancement of reflections arising from underlying myosin organization and other reflections arising from adenylate deaminase arrangement on the filament surface. Adenylate deaminase can thus be used as a specific label in the study of myosin presence and organization.