With DNA and proteins, researchers build transit for lugging molecular cargo

Artist's view of Kinesin dragging cargo down a microtubule.

Vale lab, UCSF

Humanity's just now beginning to learn how to master construction at the nanometer scale, but biology has been tinkering with this for billions of years. And as we've gotten better at manipulating biological materials, the lines between nanotechnology and synthetic biology are getting rather blurry. Over the weekend, Nature Nanotechnology released a paper that describes tiny biological machinery engineered to construct a transit system and then bring cargo to its hub. Its components? DNA and proteins.

To a certain extent, the British team behind the work wasn't engineering a system so much as re-engineering what life has evolved already. Cells have a transit system that uses structures called microtubules. These tiny fibers, 25 nanometers in diameter, are made of repeating units of two proteins (alpha and beta tubulin, naturally). There are also specialized motor proteins that bind to them and drag cargo along the fiber. This cellular transit system does everything from getting packages of proteins to the right place in the cell to ensuring that the chromosomes are split up evenly when a cell divides.

The motor protein used in these experiments is called kinesin. Each molecule of kinesin has a section where it binds cargo and a "head" that sticks to the microtubules. When two of these molecules stick together, the heads act a bit like feet, taking alternating steps along the microtubule, each stride advancing the kinesin 8nm down its length. Each of these steps uses a little bit of energy in the form of ATP. The process is shown in detail in the video below.