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1

A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky prosp. 33, 119071, Moscow, Russia

2

A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119992, Moscow, Russia





*

Author to whom correspondence should be addressed.



Abstract We compared thermally induced denaturation and aggregation of two isoforms of the isolated myosin head myosin subfragment 1, S1 containing different -essential- or -alkali- light chains, A1 or A2. We applied differential scanning calorimetry DSC to investigate the domain structure of these two S1 isoforms. For this purpose, a special calorimetric approach was developed to analyze the DSC profiles of irreversibly denaturing multidomain proteins. Using this approach, we revealed two calorimetric domains in the S1 molecule, the more thermostable domain denaturing in two steps. Comparing the DSC data with temperature dependences of intrinsic fluorescence parameters and S1 ATPase inactivation, we have identified these two calorimetric domains as motor domain and regulatory domain of the myosin head, the motor domain being more thermostable. Some difference between the two S1 isoforms was only revealed by DSC in thermal denaturation of the regulatory domain. We also applied dynamic light scattering DLS to analyze the aggregation of S1 isoforms induced by their thermal denaturation. We have found no appreciable difference between these S1 isoforms in their aggregation properties under ionic strength conditions close to those in the muscle fiber in the presence of 100 mM KCl. Under these conditions kinetics of this process was independent of protein concentration, and the aggregation rate was limited by irreversible denaturation of the S1 motor domain. View Full-Text

Keywords: myosin subfragment 1; thermal denaturation; heat-induced aggregation; differential scanning calorimetry; dynamic light scattering myosin subfragment 1; thermal denaturation; heat-induced aggregation; differential scanning calorimetry; dynamic light scattering





Autor: Denis I. Markov 1, Eugene O. Zubov 1, Olga P. Nikolaeva 2, Boris I. Kurganov 1 and Dmitrii I. Levitsky 1,2,*

Fuente: http://mdpi.com/



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