Molecular Motor Proteins Discovered in Reverse

motor proteinsMotor proteins are some of the movers and shakers inside living cells, helping out with all sorts of essential intracellular processes. Kinesin-14s are a group of motor proteins that travel along little microtubule tracks during cell division in eukaryotic cells like yours. OSU scientists have discovered a context-dependent directionality switch on KlpA, a kinesin-14 from a filamentous fungus that could one day lead to new approaches in treating certain types of cancers in humans.

When it comes time for a cell to divide, duplicated stuff like chromosomes that new daughter cells receive are separated using a whole bunch of itty bitty microtubules, making up a thing called the mitotic spindle (which is also a good band name).

OK, let’s take a break from the big-kid words a sec—here it may be helpful to picture a couple jellyfish with microtubule tentacles trying lazily to get away from each other while stuck inside the same bubble. Yeah, that sounds about right for whatever a mito-spindle whatzit looks like. Anyways, back to the news.

Scientists have known that kinesin-14s are important for the assembly and maintenance of the mitotic spindle. Until now it was believed that these little molecular motors only moved towards the minus end of whatever little microtubule they happened to be traveling in order to transport their tiny cargos. But new evidence indicates this isn’t always the case.

A particular region of this slinky-meets-doggie-bone-shaped motor protein can reverse the direction of travel depending on its surroundings and configuration. More correctly, researchers from OSU’s department of physics, department of biochemistry and biophysics, and others describe in a recent paper, “the nonmotor microtubule-binding domain likely acts as a switch for controlling the direction of KlpA motility. Collectively, these findings provide important insights into the mechanism and regulation of KlpA functions inside the mitotic spindle.” Researchers were able to make this characterization using total internal reflection fluorescence microscopy.

“KlpA is a fascinating motor protein because it is the first of its kind to demonstrate bidirectional movement,” said corresponding author Weihong Qiu in a recent OSU press release. “It provides a golden opportunity for us to learn from Mother Nature the rules that we can use to design motor protein-based transport devices. Hopefully in the near future, we could engineer motor protein-based robotics for drug delivery in a more precise and controllable manner. It’s becoming clear that KlpA-like motors in humans are crucial to cancer cell proliferation and survival. Our results help better understand other KlpA-like motor proteins including the ones from humans, which could eventually lead to novel approaches to cancer treatment.”

If you’re scratching your head right now, please, lower the left eyebrow. This is indeed hopeful news. 

By Matthew Hunt