Research: MYOSINS Folding Project #12296

These projects are attempts to better understand the behavior of a longstanding drug lead, blebbistatin, and its effects on the motor domain of skeletal muscle myosin.

Myosins are ubiquitous and their motor domains are highly conserved, so while drugging them has potential especially in the context of certain muscle related diseases like hypertrophic cardiomyopathy (a relatively prevalent form of genetic heart disease), understanding how a potential drug interacts with myosin isoforms from first principles will help seed development efforts to avoid side effects. Myosin works by cycling through an ATP hydrolysis (ATP--Adenosine Tri-Phosphate--is the energy currency of the cell, and cutting the third phosphate off hydrolitically is how that currency is spent) driven process where it binds actin, undergoes a conformational (a particular arrangement of the atoms in the protien) change, and then releases actin (allowing collections of myosins to work in concert to pull along the length of an actin fiber).

A common mode of action for inhibitors of myosin is that they will get a motor domain stuck in a particular step in the cycle.

Blebbistatin is an inhibitor that binds to a subclass of myosin at a cryptic site and inhibits phosphate release, which is a necessary step in the cycle. To understand how blebbistatin impacts the conformations the protein can access, we've started simulaitons from four different chemical compositions:

• 12296: Blebbistatin only.

  All other binding sites are vacant.

  Experimentally, blebbistatin is believed to not bind this state.

  We hope to see what impact it may have on the ATP/ADP+Phosphate binding site.

• 12297: ADP, Phosphate, and Blebbistatin.

  This is thought to be the mode of action of blebbistatin.

  It causes the Phosphate present in this conformation to be held more tightly, thus preventing the enzyme from cycling.

• 12298: ADP and Blebbistatin.

  This simulation will allow us to ask what is different about the phosphate binding site when Blebbistatin is present, to see if it maintains conformations that would bind phosphate well even when it is no longer present.

• 12299: ADP only.

  To see how the blebbistatin binding site fluctuates when the phosphate is not present.

  Because blebbistatin is supposed to be selective for the states that are compatible with phosphate binding, this will help us elucidate the coupling between the two sites.