Type of Document	Dissertation
Author	Baumann, Bruce A.
URN	etd-08312003-194231
Title	Studies on the Structures and Function of the Myosin Head
Degree	Doctor of Philosophy
Department	Physics, Department of
Advisory Committee	Advisor Name Title Tim Logan Committee Chair David Van Winkle Committee Member Kenneth A. Taylor Committee Member Nancy L. Greenbaum Committee Member Peter Fajer Committee Member
Keywords	The mechanism by which muscle generates force
Date of Defense	2003-06-01
Availability	unrestricted
Abstract The mechanism by which muscle generates force has been the subject of considerable study. Key to our understanding of this mechanism is the conformational changes occurring in the myosin "head" as it interacts with the thin filament. Each myosin head individually binds to the thin filament, hydrolyzes ATP and generates force. This study has used electron paramagnetic resonance (EPR) spectroscopy to study the structure and function of the regulatory domain located on the distal portion of the myosin head. Skeletal myosin S1 was labeled with a variety of lysine targeting spin labels, under conditions optimized to label the reactive lysine residue Lys-83, to determine if spin label suitable for EPR studies could be found. Two spin labels (HO-226 and HO-2095T) had ordered populations. Competitions, of the two labels with selective blocking agents, determined that they were labeling both lysine and cysteine residues. The anisotropy for both labels was found to derive from labeled cysteine residues not Lys-83, rendering both unsuitable for EPR studies of myosin S1 The mobility of the essential light chain (ELC) and the regulatory light chain (RLC) subdomains of the regulatory domain was individually measured utilizing saturation transfer electron paramagnetic resonance (ST-EPR) spectroscopy. Their mobilities were found to be similar, and that similarity persisted under conditions, which increase the overall mobility of the myosin head: upon RLC phosphorylation, an increase of pH or the presence of divalent cations. Modeling of this mobility enabled calculation of the persistence length of the regulatory domain, which at 1.5 µm, is adequate for it to serve as a lever arm. This is consistent with theories of force generation where the regulatory domain serves as a lever to amplify movement of the catalytic domain during the power stroke of striated muscle.
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