How are myosin fragments bound to nitrocellulose film?

In an attempt to identify the binding sites of myosin fragments to the nitrocellulose film in a flow cell, proteolytic digestion was performed of myosin fragments bound to the substrate. Chymotryptic digestion of papain.Mg-subfragment-1 (S1) showed that a large proportion of S1 were bound near the tail and that the digestion site was protected for some S1. The binding of S1 near the tail was also confirmed by the production of extra long subfragment-2 (S2) by chymotryptic digestion of heavy meromyosin (HMM). Papain digestion of HMM released slightly smaller HMM from the substrate and impaired the motility at the same time. Hence, the motility of HMM is supported largely by those bound to the substrate near the C terminus. These results demonstrate the importance of flexible regions of myosin in generating active movements.