New measurements performed at the University of Illinois at Urbana-Champaign have shown that one of these molecular motors, myosin VI, can function individually as anchors or in pairs as transporters. The new results have helped to resolve a research controversy and better explain how these little proteins perform their duties.
"Myosin VI is a tiny molecule that converts chemical energy into mechanical motion and transports its load by 'stepping' along filaments of actin," said Paul Selvin, a John Bardeen Faculty Scholar of Physics at Illinois and a co-author of a paper to appear in the Feb. 3 issue of the journal Molecular Cell. "Our measurements prove that molecules of myosin VI can naturally form pairs and then go for walks while carrying cargo."
In 2004, Selvin and colleagues at Illinois and at the University of Pennsylvania reported that myosin VI moved by a "hand-over-hand" mechanism in steps of approximately 60 nanometers. (One nanometer is a billionth of a meter, or about 10,000 times smaller than the width of a human hair).
"In that experiment, we took two myosin VI monomers and 'zippered' their tops together to form a dimer which then walked along the actin," Selvin said. "Some researchers thought that by forcing the molecules to dimerize, our results were not representative of what occurs naturally. Other researchers claimed that myosin VI was always a monomer. We have now shown that these molecules can indeed come together and dimerize on their own."
In the latest experiment, the researchers repeated their earlier measurement, but without zippering the monomers together. They used a high-precision mea
Contact: James E. Kloeppel, Physical Sciences Editor
University of Illinois at Urbana-Champaign