Premium
Do thin filaments of smooth muscle contain calponin?
Author(s) -
Nishida Wataru,
Abe Masahiro,
Takahashi Katsuhito,
Hiwada Kunio
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80999-y
Subject(s) - calponin , tropomyosin , actin , caldesmon , myosin , protein filament , biophysics , chemistry , atpase , biochemistry , biology , enzyme , calmodulin
A new method for the preparation of smooth muscle thin filaments which include calponin was established. We found that calponin readily separated from thin filaments in the presence of 10 mM ATP. By preventing thin filament extract from exposing to ATP, we obtained thin filaments which contained actin, tropomyosin, caldesmon and calponin in molar ratios of 7:0.9:0.6:0.7. We studied myosin Mg‐ATPase activity by using the thin filaments in comparison with classical thin filaments prepared by the method of Marston and Smith, which contained the same amounts of caldesmon and tropomyosin as our thin filaments but lost almost all calponin. The presence of calponin reduced the V max value for thin filament‐activated myosin Mg‐ATPase activity by 33% without a significant change in K m value. These findings suggest that calponin inhibits myosin Mg‐ATPase activity by modulation of a kinetic step as an integral component of smooth muscle thin filaments.