Abstract
A subfragment of myosin A [EC 3. 6. 1. 3] was isolated from tryptic digest of HMM by column chromatography on DEAE-cel-lulose. Approximately 40 percent of HMM mass was converted into an enzymatically active, relatively homogeneous component. This process is accompanied by a large change in viscosity from 0.47 to 0.085 dl./g. Sedimentation diagram revealed a relatively high degree of homogeneity and s020, W was 6.2S. The viscosity measurement indicated a low particle assymmetry. Molecular weight of the subfrag-ment was estimated as 1.47×105 from the Scheraga-Mandelkern equation.
No significant difference in properties of ATP and ITP hydrolysis of the subfragment from those of HMM was observed at various pH values. The function of SH-group in the ATPase activity of the subfragment was essentially similar to that of HMM.
The subfragment did not accelerate the polymerization of G-actin, though binding of the subfragment to F-actin was variable from preparation to preparation so far.
We wish to thank Dr. Y. Tonomura for valuable criticisms.
