Myosin subfragment 1 (S1) was prepared from the ordinary muscle of tilapia Oreochromis niloticus by a-chymotryptic digestion in the presence of EDTA. S1 was further separated by anion-exchange column chromatography into two isozymes, based on associating alkali light chains A1 and A2, S1(A1) and S1(A2). The two isozymes exhibited a similar pH-dependency of Ca- or EDTA-ATPase activity, with a minimum at around pH 7 for the former activity and a maximum at around pH 9 for the both. As a whole, however, both activities of S1(A2) were somewhat higher than those of S1(A1). In actin-activated Mg-ATPase activity, on the other hand, S1(A2) showed a lower apparent dissociation constant for actin and higher maximum velocity than S1(A1), in contrast to the counterpart of rabbit. All these results suggest that alkali light chains affect S1 ATPases both in the presence and absence of actin.
ASJC Scopus subject areas
- Aquatic Science