Send to

Choose Destination
Biochemistry. 1998 Feb 17;37(7):1969-78.

Interaction of actin and ADP with the head domain of smooth muscle myosin: implications for strain-dependent ADP release in smooth muscle.

Author information

Department of Biochemistry and Biophysics, Washington State University, Pullman 99164, USA.


Transient kinetic methods were used to study interactions between actin, MgADP, and smooth muscle (chicken gizzard) myosin subfragment 1 (smS1). The equilibrium dissociation constant (Kd) of actin for smS1 was 3.5 nM, tighter than that of skeletal S1 (skS1). Actin binding to smS1 was weakened 5-fold by saturation with ADP compared to 30-60-fold for skS1. The Kd of ADP for smS1 was increased from 1.2 to 5 microM by actin, whereas for skS1 values increased from 2 to 100 microM. Thus, coupling between ADP and actin binding is weaker for smS1. Previous studies show that release of ADP from actin.smS1.ADP produces a tilt of the regulatory domain [Whittaker, M., Wilson-Kubalek, E. M., Smith, J. E., Faust, L., Milligan, R. A., and Sweeney, H. L. (1995) Nature 378, 748-751]. This result was confirmed by independent structural methods; tilting was absent for skS1, and the Kd for ADP was in agreement with the values measured here [Gollub, J., Cremo, C. R., and Cooke, R. (1996) Nat. Struct. Biol. 3, 796-802; Poole, K. I. V., Lorenz, M., Ellison, P., Evans, G., Rosenbaum, G., Boesecke, P., Holmes, K. C., and Cremo, C. R. (1997) J. Muscle Res. Cell Motility 18, 264]. We discuss tilting upon ADP release with respect to our measurements, previous measurements with skS1, and nucleotide concentrations in smooth muscle. We propose that these data suggest a strain-dependent ADP release mechanism that may be accentuated in smooth muscles.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center