Novel intermolecular surface force reveals actomyosin driving mechanism

November 7, 2017, Tohoku University
A novel force generation mechanism of actomyosin.An actin filament (F-actin) produces an electric field (black arrows) as high as 100 MV/m around F-actin due to its negative surface charges. The water molecules in such a high electric field become hyper-mobile water molecules (HMW, light green) in close proximity of F-actin. On the other hand, ATP in solution binds with a myosin head (orange) and is split into adenosine diphosphate (ADP) and inorganic phosphate (Pi) in the head. When the myosin head with ADP and Pi binds with F-actin (orange red), several actin subunits change their structures (beige). Then the electric field strength decreases around these changed actin subunits and the HMW intensity also decreases (light blue) to become close to free water. In the present study, the protein hydration state has been found to be more stable in the stronger HMW region. In the figure, the myosin head is driven to the right where the HMW intensity is stronger (light green), with detaching from F-actin and attaching again with F-actin. The force evaluated by the present method is as high as several piconewtons, which is on the level of the experimental values. This can be a principle of novel surface force acting between a charged macromolecule, such as protein and DNA, and a solute protein widely applicable to science and technology. Credit: Makoto Suzuki

The actin and myosin complex (actomyosin) generates contraction force of a muscle utilizing the adenosine triphosphate (ATP) hydrolysis reaction. Many attempts have thus been made to explain the molecular origin of the actomyosin motility.

A power stroke model, proposed by Huxley and Simmons in 1971, initiated much research including atomic-structure studies and the investigation of the molecular biology of myosin and actin molecules. The power stroke model, modified lately, is widely adopted in standard biology textbooks.

However, there remains a serious problem. According to the experimental thermodynamics data, the ATP hydrolysis in the myosin head does not produce a myosin state with high enough energy to generate the contraction force.

Now, a research group, led by Emeritus Professor Makoto Suzuki at Tohoku University in collaboration with Professor Nobuyuki Matubayasi at Osaka University, has succeeded in explaining the actomyosin driving mechanism according to the experimental thermodynamics data.

In the study, the water structure in close proximity of an actin filament (F-actin) is modified upon binding with a myosin head hydrolyzing ATP to F-, that leads to a change in the affinity to the myosin head and thus to the generation of the driving force of actomyosin.

The presence of the novel intermolecular surface force - which was demonstrated for the first time based on the present hydration analyses - was a marked discovery. This article is, therefore, the first to successfully unveil the actomyosin driving mechanism by introducing a novel intermolecular surface .

Explore further: Atomic resolution of muscle contraction

More information: Makoto Suzuki et al, Physical driving force of actomyosin motility based on the hydration effect, Cytoskeleton (2017). DOI: 10.1002/cm.21417

Related Stories

Atomic resolution of muscle contraction

March 8, 2017

At the molecular level, muscle contraction is defined by myosin molecules pulling actin filaments. New electron cryomicroscopy images with unprecedented resolution taken by researchers at Osaka University reveal unexpectedly ...

Biophysics: Order in chaos

May 3, 2012

The process of skeletal muscle contraction is based around protein filaments sliding inside sarcomeres — the structural units of muscle fiber. Inside each sarcomere is a set of filament motors, which appear in different ...

Peering under the hood into the workings of molecular motors

December 21, 2015

Understanding how tiny molecular motors called myosins use energy to fuel biological tasks like contracting muscles could lead to therapies for muscle diseases and cancers, says a team of researchers led by Penn State College ...

Recommended for you

Nanoscale Lamb wave-driven motors in nonliquid environments

March 19, 2019

Light driven movement is challenging in nonliquid environments as micro-sized objects can experience strong dry adhesion to contact surfaces and resist movement. In a recent study, Jinsheng Lu and co-workers at the College ...

OSIRIS-REx reveals asteroid Bennu has big surprises

March 19, 2019

A NASA spacecraft that will return a sample of a near-Earth asteroid named Bennu to Earth in 2023 made the first-ever close-up observations of particle plumes erupting from an asteroid's surface. Bennu also revealed itself ...

The powerful meteor that no one saw (except satellites)

March 19, 2019

At precisely 11:48 am on December 18, 2018, a large space rock heading straight for Earth at a speed of 19 miles per second exploded into a vast ball of fire as it entered the atmosphere, 15.9 miles above the Bering Sea.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.