Key result
Native LC2-free myosin subfragment 1 reversibly dimerizes at low temperatures and dissociates at high temperatures.
Why the study?
The existence and characteristics of the native myosin LC2-free subfragment 1 (S1) dimer were reinvestigated due to uncertainty about its presence and properties.
Answers are grounded in this paper and cite their sources.
Biophysical parameters for S1 monomer and dimer refine hydrodynamic models; leaves open native dimer prevalence in vivo.
We reinvestigated whether the native myosin LC2-free-subfragment 1 (S1) dimer exists by using viscometry, capillary electrophoresis, and laser light scattering. We found that the intrinsic viscosity of the monomer is [eta]m = 6.7 cm3/g and its translation diffusion coefficient is (c = 0) = 4.43 x 10(-)7 cm2/s. For the dimer, [eta]d = 19.8 cm3/g and (c = 0) = 2.54 x 10(-)7 cm2/s. Using the Svedberg equation and introducing the values of the sedimentation coefficients (5.05 S for the monomer and 6.05 S for the dimer), we find the following molecular weights: Mr,m = 108 000 Da and Mr,d = 213 000 Da, which agree well with previous determinations. Capillary electrophoresis successfully separated S1(A1) and S1(A2), in a monomer buffer, and S1(A1) and S1(A2) and a heterodimer S1(A1)-S1(A2), in a dimer buffer. An interesting feature of the monomer-dimer equilibrium is the presence of temperature transitions, whose positions and widths depend upon the buffer conditions. At low temperatures, a pure dimer was observed, whereas at high temperatures only the monomer was present. The dimerization site on both myosin and S1 is extremely labile.
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Morel et al. (1998) studied this question. Myosin LC2-free subfragment 1 (S1) was evaluated on Dimerization properties (intrinsic viscosity, translation diffusion coefficient, molecular weight). Native myosin LC2-free subfragment 1 exists as a dimer at low temperatures and a monomer at high temperatures, with distinct intrinsic viscosities and molecular weights.
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