D. Lorinczy et J. Belagyi, Functional and structural differences in skeletal and cardiac myosins. A molecular dynamic approach, THERMOC ACT, 343(1-2), 2000, pp. 27-33
Conventional and saturation transfer electron paramagnetic resonance spectr
oscopy and differential scanning calorimetry were used to study the interna
l dynamics and stability of cardiac myosin.
Intact and LC 2-deficient myosin isolated from bovine heart were spin-label
led with maleimide and iodoacetamide probe molecules at the SH1 sites. It w
as found that the probe molecules rotate with an effective rotational corre
lation time of 42 ns, which is at least six times shorter than the rotation
al correlation time of the same label on skeletal myosin. Addition of MgADP
induces intrinsic changes in the multisubunit structure of myosin, but it
does not lead to changes of the overall rotational properties of the myosin
head.
Temperature dependence of the EPR spectra of maleimide-labelled myosin show
s continuous decrease of the spectral parameters (intensity ratio of the pe
ak heights, hyperfine splitting) at increasing temperature. However, marked
changes were obtained at about 16 degrees C in LC 2-deficient myosin. DSC
measurements also support the view that the removal of the LC 2 light chain
produces change in the internal structure of cardiac myosin. (C) 2000 Else
vier Science B.V. All rights reserved.