Kinesins are a family of motor proteins found in multicellular organisms. They function as 'little engines' within the cells and transport molecular cargo along microtubules, among other activities. The microtubules -- 25 nanometers thick or one ten- thousandth the diameter of a human hair -- are hollow cylinders of the protein tubulin. They are extremely dynamic and have the ability to grow and shrink as the cell changes shape.
"We are trying to get under the hood of these motors and understand what makes their sequences unique," said William Hancock, professor of biomedical engineering, Penn State. "Because they carry out so many vital functions in the cells of the body, we really want to understand how they operate at the molecular level."
In total, there are 45 different kinesin motor proteins in humans. Hancock and Yalei Chen, graduate student in cell and developmental biology, Penn State's Huck Institute of the Life Sciences, tracked the movements of individual fluorescently-tagged kinesin-5 molecules in the laboratory and found that the motor pauses at the end of the microtubules. It then generates pushing forces, which slide the microtubules apart and essentially allow the motor to grow the microtubules. The researchers reported their results in a recent issue of Nature Communications.