Molecular freight: Synthetic nanoscale transport system modeled on nature

December 21, 2009

( -- Just like our roads, there is a lot of traffic within the cells in our bodies, because cell components, messenger molecules, and enzymes must also be brought to the right places in the cell. One of these transportation systems functions like a kind of railway: a system of molecular tracks is used to transport vesicles and their contents to their target destinations.

In imitation of this natural “cargo transport”, Japanese researchers have developed a synthetic molecular transport system. The scientists, led by Youichi Tsuchiya and Seiji Shinkai, report in the journal that this could form the basis for the development of a method for transporting therapeutic genes into .

The cellular rail system uses actin filaments for tracks. Actin filaments are strong strands of protein that form a network inside a cell. Acting as both and wheels are myosin molecules, which move along the tracks. The vesicle being transported hangs on to the tail end of the myosin. The myosin head consists of ATPase, an enzyme that degrades ATP. ATP is cellular fuel; its decomposition releases energy. In the process of splitting the ATP, the angle of the myosin head attached to the actin filament changes, which causes the myosin to move along the filament like a wheel on a track, bringing its cargo along for the ride.

The researchers also incorporated actin, myosin, and ATP as components for their synthetic transport system. For their container, they chose schizophyllan, a triple-stranded helical from fungi. In certain solvents the helix unravels; when placed back in water, the polysaccharide twists back up into a helix. In this process, it can wrap around large molecules or , packaging them up. In their study, the researchers loaded these molecular containers with carbon nanotubes. They used cobalt ions to dock on several myosin units, and these wheels did indeed move the tiny freight train along the actin track. With an average speed of about 95 nm/s, the freight cars crossed the amazing distance of about 5 µm.

Transport along cellular actin tracks always moves in only one direction. The filaments are bound to each other at junctions, creating a transportation network that also allows for changes in direction within the cell. The synthetic molecular freight trains can also change from one filament to another at junctions in the network. Because the direction of the actin track leads into the cell nucleus, the artificial transport system may be useful in gene therapy, because it could wrap up the therapeutic genes and carry them into the cellular nucleus.

Explore further: Tidy motor protein folds away when the job is done

More information: Seiji Shinkai, A Polysaccharide-Based Container Transportation System Powered by Molecular Motors, Angewandte Chemie International Edition,

Related Stories

Tidy motor protein folds away when the job is done

October 3, 2006

A discovery by University of Leeds researchers has revealed how a motor protein shuts itself down and becomes compact when it has no cargo to carry. It then goes in search of more cargo, perhaps carried by other passing proteins.

Molecular motors may speed nutrient processing

May 30, 2007

Matthew Tyska, Ph.D., recalls being intrigued, from the first day of his postdoctoral fellowship in 1999, with a nearly 30-year-old photograph. It was an electron micrograph that showed the internal structures of an intestinal ...

How actin networks are actin'

January 2, 2008

Dynamic networks of growing actin filaments are critical for many cellular processes, including cell migration, intracellular transport, and the recovery of proteins from the cell surface. In this week’s issue of the open-access ...

A budding role for a cellular dynamo

February 18, 2009

Actin, a globular protein found in all eukaryotic cells, is a workhorse that varies remarkably little from baker's yeast to the human body. Part of the cytoskeleton, actin assembles into networks of filaments that give the ...

Recommended for you

Hydrogels can put stem cells to sleep

February 10, 2016

Unlike normal cells, stem cells are pluripotent—they can become any cell type, which makes them powerful potential treatments for diseases such as diabetes, leukemia and age-related blindness. However, maintaining this ...

'Molecular movie' opens door to new cancer treatments

February 9, 2016

An international team of scientists led by the University of Liverpool has produced a 'structural movie' revealing the step-by-step creation of an important naturally occurring chemical in the body that plays a role in some ...

Room-temperature lithium metal battery closer to reality

February 4, 2016

Rechargeable lithium metal batteries have been known for four decades to offer energy storage capabilities far superior to today's workhorse lithium-ion technology that powers our smartphones and laptops. But these batteries ...


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.