MYOSIN SUBFRAGMENT-1 IS FULLY EQUIPPED WITH FACTORS ESSENTIAL FOR MOTOR FUNCTION

The sliding velocity of actin filaments propelled by chicken skeletal myosin subfragment-l (S1) was measured when the tail end of S1 was spe cifically bound to the glass surface. To achieve the specific binding, a regulatory light chain was replaced by a recombinant fusion protein of biotin-dependent transcarboxylase (BDTC) and chicken gizzard smoot h muscle regulatory light chain (cgmRLC). The BDTC-cgmRLC of S1 was th en attached to the glass surface using a biotin-avidin system. The vel ocity of actin filaments caused by S1 bound to the surface in this man ner was 6.81+/-0.6 mu m/sec at 29 degrees C, which was 3.5-fold greate r than that (1.9+/-0.3 mu m/sec) when bound directly to the surface as in previous studies, but similar to that caused by native chicken ske letal myosin (6.5+/-0.6 mu m/sec). The actin-activated Mg-ATPase activ ity was similar to that of S1 before the RLC of S1 was exchanged for B DTC-cgmRLC. The results indicate that S1 can produce a normal fast mov ement of actin filaments as well as hydrolyse ATP and generate force. (C) 1997 Academic Press