Discussion: Interaction of C-Protein with Myosin and Light Meromyosin

In connection with the study of C-protein reported here by Gerald Offer, I wish to report briefly some observations of the effects of C-protein on the electron microscopic appearance of artificial myosin filaments and light meromyosin para-crystals. Upon dialysis to low ionic strength, myosin which has been purified by DEAE-Sephadex chromatography forms very long filaments (up to 10-20 microns) with an exceptionally uniform diameter and regular appearance, as illustrated in Fig. 1A. In many cases an axial periodicity of about 14.5 nm can be seen in the micrographs and measured by optical diffraction. It is usually impossible to find a bare zone in these filaments, although short filaments formed from the same myosin by rapid dilution of the ionic strength do show a normal bipolar structure.