Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Leslie A. Leinwand

Second Advisor

Thomas Perkins

Third Advisor

Andreas Hoenger

Fourth Advisor

Michael Stowell

Fifth Advisor

Hector Rodriguez

Abstract

Biophysical and biochemical imbalance of mechanisms relevant to muscle function, can result in morphological changes to the tissue. While the purpose of activities involving exercise is to modify the shape and size of skeletal muscle, and the length of these muscles allows wide ranges of stiffness and stretch to be applied, cardiac tissue is not meant to change much. However, stressful extrinsic factors (poor diet, chemotherapy, etc) or intrinsic factors like inherited mutations in muscle functioning genes can result in a myopathy or a disease of the muscle. In fact, another biological process that requires much compliance of many molecules is embryogenesis. Although the timeline of an embryonic structure is limited, compared to an adult heart and muscle composition, continuous and coordinated movement is essential, but cumulative, prolonged disruptions can be harmful. At the core of muscle biology is the myosin molecule which is a motor protein that hydrolyzes ATP, binds to actin, and the spatial dynamics of its function (contraction-relaxation) alter the length of muscle. Myosin cyclically follows specific steps and undertakes well-defined structural conformations during these events, but mutations can alter the time and stability of any of these aspects. In this thesis I did a comprehensive analysis of the ATPase cycle parameters for both embryonic and cardiac myosin and studied the effects of specific associated or linked mutations have on function. The multiple mutations were in the interest of cataloging common features and defects to identify mechanistic patterns. In a collaborative effort I also used these wet-lab measurements to simulate the cycle using a working kinetic model for the myosin ATPase cycle. We have found distinct differences between three different myopathies that will be discussed in the following chapters.

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