# Myosin Movement In Vitro - Molecular Characterization

> **NIH NIH R01** · STANFORD UNIVERSITY · 2021 · $599,415

## Abstract

Abstract
Myosin molecular motors play crucial, dynamic roles in most cellular processes, including contraction,
movement, and shape change. A variety of diseases owe their origins to defects in the myosin family of
molecular motors. A prime example is inherited familial hypertrophic cardiomyopathy (HCM), which leads to
hyper-contractility of the heart. HCM results from mutations in various cardiac muscle proteins, with mutations
in β-cardiac myosin and its associated thick filament protein myosin binding protein C (MyBPC) accounting for
about 80% of these cases. HCM is not rare, affecting as many as 1 in 200 people.  Current therapeutic
interventions for cardiomyopathies are limited to symptomatic relief, in large part because the molecular
underpinnings of the disease – how mutations affect the biomechanical interaction of myosin with its
sarcomeric partners, and thus sarcomeric force, velocity, and power output – are not well understood. Studies
using human β-cardiac myosin have shown that mutation-induced changes in the basic biochemical and
biomechanical parameters of the myosin motor do not adequately account for the cardiac hypercontractility
that is a clinical hallmark of HCM. Rather, it has recently been shown that HCM-causing mutations in the
myosin motor domain disrupt intramolecular interactions that stabilize a folded-back, off state of myosin. This
results in an increase in the number of heads functionally accessible to interact with actin, which in turn may
lead to hypercontractility. In this proposal, the effects of HCM-causing point mutations in different regions of
human β-cardiac myosin will be explored, including the motor domain and both the proximal and distal portions
of the alpha-helical coiled coil tail that allows myosin to form bipolar thick filaments. The interaction of myosin
with MyBPC has also been implicated in regulation of the folded-back state of myosin. The effects of potential
physiological regulators of this interaction, including phosphorylation and calcium binding, will be assessed
using binding and functional assays. The effects of point mutations in different regions of myosin and in
different domains of MyBPC will also be determined. Finally, a variety of structural approaches will be
employed to determine the structure of the folded-back state of myosin in the absence and presence of
MyBPC. Both negative stain and cryo-electron microscopy will be used to study the folded-back form of myosin
and the myosin-MyBPC complex, and this work will be supplemented by cross-linking mass spectrometry to
define interfacial residues. FRET probes will be placed on the human β-cardiac myosin to observe its transition
between the on-and-off states. This measurement will be critical in the HCM mutant myosins which have been
shown to disrupt the off-state of myosin. Transient time-resolved FRET measurements will enable us to
measure the nanosecond dynamics of myosin as it undergoes the on-to-off transition. Thus, we will u...

## Key facts

- **NIH application ID:** 10121688
- **Project number:** 2R01GM033289-37
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Aaron F Straight
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $599,415
- **Award type:** 2
- **Project period:** 1984-04-01 → 2025-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10121688

## Citation

> US National Institutes of Health, RePORTER application 10121688, Myosin Movement In Vitro - Molecular Characterization (2R01GM033289-37). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10121688. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*