Strategic Communications and Marketing News Bureau

Molecular motor Myosin VI moves ‘hand over hand,’ researchers say

Myosin VI (blue) is a molecular motor that walks "backwards" on filaments of actin (red). By labeling a myosin VI on the head (green), or on the neck (red), and localizing the dye within a few nanometers, scientists determined that myosin walks "hand-over-hand," while causing a part of the protein to come undone.

Myosin VI (blue) is a molecular motor that walks “backwards” on filaments of actin (red). By labeling a myosin VI on the head (green), or on the neck (red), and localizing the dye within a few nanometers, scientists determined that myosin walks “hand-over-hand,” while causing a part of the protein to come undone.

CHAMPAIGN, Ill. – In the human body, hundreds of different types of biomolecular motors help carry out such essential tasks as muscle contraction, moving chromosomes during cell division, and reloading nerve cells so they can repeatedly fire.

How these little proteins perform their duties is becoming clearer to scientists using an extremely sensitive measurement technique. Myosin VI, they found, moves by the same “hand-over-hand” mechanism as two other molecular motors, myosin V and kinesin.

“Now that a third molecular motor has been found to move in the same hand-over-hand fashion, the argument for a rival ‘inchworm’ motion is getting pretty weak,” said Paul Selvin, a professor of physics at the University of Illinois at Urbana-Champaign and a co-author of a paper to appear in the Journal of Biological Chemistry.

Physics professor Paul Selvin has found another molecular motor that uses the hand-over-hand model of movement.

Physics professor Paul Selvin has found another molecular motor that uses the hand-over-hand model of movement.

Myosin VI is a reverse-direction molecular motor that moves materials to various locations within a living cell. Like the related protein myosin V, myosin VI has two “arms” connected to a “body.” The tiny molecule converts chemical energy into mechanical motion, and transports its load by “stepping” along polarized filaments of actin – but in the opposite direction from other myosin variants.

“Studies have suggested two main models for the stepping movement,” Selvin said. “One is the hand-over-hand model in which the two arms alternate in the lead. The other model is the inchworm model in which one arm always leads.”

To examine the myosin VI stepping mechanism, the researchers applied the same technique that was used to study both myosin V and kinesin. Called FIONA – Fluorescence Imaging with One Nanometer Accuracy – the measurement technique can track the position of a single molecule to within 1.5 nanometers. (One nanometer is a billionth of a meter, or about 10,000 times smaller than the width of a human hair).

Selvin excites molecules with a laser.

Selvin excites molecules with a laser.

“First, we attached a small fluorescent dye to one of the arms and took a picture with a digital camera attached to a microscope to find exactly where the dye was,” Selvin said. “Then we fed the myosin a little food called adenosine triphosphate, and it took a step. We took another picture, located the dye, and measured how far the dye moved.”

By examining the step size, the scientists could determine whether the protein used a hand-over-hand mechanism or an inchworm mechanism for movement. “The average step size for the myosin VI arm was approximately 60 nanometers, while the molecule’s center of mass moved only half that distance,” Selvin said. “This clearly indicated that a

hand-over-hand model was being employed.”

Surprisingly, myosin VI has a step size that is highly variable, but on average is nearly as large as that of myosin V, which has a lever arm that is three times longer.

“For myosin VI to reach the same distance, the molecule must somehow come apart and then snap together again,” Selvin said. “To understand how it accomplishes this feat will require further study.”

The co-authors of the paper are Selvin, Hyokeun Park and Ahmet Yildiz at Illinois, and Li-Qiong Chen, Dan Safer, H. Lee Sweeney and Zhaohui Yang at the University of Pennsylvania. The National Institutes of Health funded the work.

Read Next

Life sciences Portrait of the research team posing together.

Minecraft players can now explore whole cells and their contents

CHAMPAIGN, Ill. — Scientists have translated nanoscale experimental and computational data into precise 3D representations of bacteria, yeast and human epithelial, breast and breast cancer cells in Minecraft, a video game that allows players to explore, build and manipulate structures in three dimensions. The innovation will allow researchers and students of all ages to navigate […]

Arts Photo of seven dancers onstage wearing blue tops and orange or yellow flowing skirts. The backdrop is a Persian design.

February Dance includes works experimenting with live music, technology and a ‘sneaker ballet’

CHAMPAIGN, Ill. — The dance department at the University of Illinois Urbana-Champaign will present February Dance 2025: Fast Forward this week at Krannert Center for the Performing Arts. February Dance will be one of the first performances in the newly renovated Colwell Playhouse Theatre since its reopening. The performances are Jan. 30-Feb. 1. Dance professor […]

Honors portraits of four Illinois researchers

Four Illinois researchers receive Presidential Early Career Award

CHAMPAIGN, Ill. — Four researchers at the University of Illinois Urbana-Champaign were named recipients of the Presidential Early Career Award for Scientists and Engineers, the highest honor bestowed by the U.S. government on young professionals at the outset of their independent research careers. The winners this year are health and kinesiology professor Marni Boppart, physics professor Barry Bradlyn, chemical and biomolecular engineering professor Ying […]

Strategic Communications and Marketing News Bureau

507 E. Green St
MC-426
Champaign, IL 61820

Email: stratcom@illinois.edu

Phone (217) 333-5010