Actin-Myosin Interaction: Structure, Function and Drug Discovery.

Piyali Guhathakurta,David Thomas,Ewa Prochniewicz

doi:10.3390/ijms19092628

Piyali Guhathakurta, David Thomas + Show 1 more

Open Access

https://doi.org/10.3390/ijms19092628

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Abstract

Actin-myosin interactions play crucial roles in the generation of cellular force and movement. The molecular mechanism involves structural transitions at the interface between actin and myosin’s catalytic domain, and within myosin’s light chain domain, which contains binding sites for essential (ELC) and regulatory light chains (RLC). High-resolution crystal structures of isolated actin and myosin, along with cryo-electron micrographs of actin-myosin complexes, have been used to construct detailed structural models for actin-myosin interactions. However, these methods are limited by disorder, particularly within the light chain domain, and they do not capture the dynamics within this complex under physiological conditions in solution. Here we highlight the contributions of site-directed fluorescent probes and time-resolved fluorescence resonance energy transfer (TR-FRET) in understanding the structural dynamics of the actin-myosin complex in solution. A donor fluorescent probe on actin and an acceptor fluorescent probe on myosin, together with high performance TR-FRET, directly resolves structural states in the bound actin-myosin complex during its interaction with adenosine triphosphate (ATP). Results from these studies have profound implications for understanding the contractile function of actomyosin and establish the feasibility for the discovery of allosteric modulators of the actin-myosin interaction, with the ultimate goal of developing therapies for muscle disorders.

Highlights

A principal challenge in the biophysics of motility is to understand the molecular mechanism by which motor proteins such as myosin convert chemical energy to mechanical work through cyclic interaction with actin filaments
During the actin-myosin ATPase cycle, myosin alters its affinity for actin in a nucleotide-dependent manner from weak (W) actin-binding states [with adenosine triphosphate (ATP) or adenosine diphosphate.phosphate (ADP.P) bound to the myosin active site] to strong (S) actin-binding states, resulting in the generation of force
We showed that the structural transition in the presence of ATP was different for myosin containing A1 and A2 isoforms of the ELC, which differ by a 45-residue N-terminal extension on A1

Summary

Introduction

A principal challenge in the biophysics of motility is to understand the molecular mechanism by which motor proteins such as myosin convert chemical energy to mechanical work through cyclic interaction with actin filaments. This biosensor was able to resolve the important structural difference between two actomyosin complexes containing different isoforms of ELC. We focused on a mutation in human ventricular (hVELC), E56G, which causes HCM [41] We hypothesized that this mutation, located near the interface of heavy and light chains, seen, affects cardiac function by altering the structural states of the actin-myosin complex during the ATPase cycle. This TR-FRET biosensor is a valuable tool for providing direct insight into the subtle structural effects caused directly by a disease-causing HCM mutation

Application of TR-FRET for Drug Discovery

Findings

Conclusions