Molecular motors and brakes work together in cells

January 30, 2007
Molecular motors and brakes work together in cells
Daughter microtubule (red) being formed on mother microtubule (red), within yeast cell (dashed line). Green represents the molecular motors, the kinesin proteins klp2, of each microtubule. Credit: Phong Tran, PhD, University of Pennsylvania School of Medicine

Researchers at the University of Pennsylvania School of Medicine have discovered that microtubules -- components responsible for shape, movement, and replication within cells -- use proteins that act as molecular motors and brakes to organize into their correct structure. If microtubules are not formed properly such basic functions as cell division and transport can go wrong, which may have implications in such disease processes as cancer and dementia.

The study, published in the January issue of Cell, is featured on the cover of that issue.

"Up until now motors and brakes were studied separately from microtubules," says senior author Phong Tran, PhD, Assistant Professor of Cell and Developmental Biology. "This study lets us have a more complete picture."

Microtubules are structures that help give shape to many types of cells, form the spindle -- a structure important in cell division -- and act as a railroad, of sorts, upon which molecular motors move protein packages for waste removal and nerve transmission.

In the Cell study, the investigators, working with fission yeast cells, showed that stable end-to-end arrays of microtubules can be achieved by a balance between the sliding by a molecular motor called klp2p and the braking of a microtubule-associated protein (MAP) called ase1p. Specifically, they showed that a preexisting "mother" microtubule acts as a platform on which a new microtubule can be formed. The new "daughter" microtubule grows and moves along the mother microtubule. In time, the daughter grows beyond the end of the mother to ultimately produce two microtubules, connected by the cross-linking MAP ase1p.

"Imagine that the daughter microtubule is a short train on the track of the mother microtubule," explains Tran. "The molecular motor is the train's engine, but the problem is that the cargo -- the molecular brakes -- gets longer, slowing down the daughter train. But when the train gets to the end of the track it remains attached to the end of mother microtubule. At the tail end, it stops moving and that defines the region of overlap. Our work shows that the cell can make microtubule structures of defined lengths stable by coordinating the sliding of the motors and the slowing of the brakes."

If microtubule-based structures are not formed properly because of failures in brakes or motors, such basic functions as cell division and cell transport can go awry, with such diseases as cancer and dementia possibly resulting. "For the first time we have shown how MAPs and motors work together in a mechanistic way," says Tran. "This is important and it will make other people who study microtubules rethink how they study the cell."

Source: University of Pennsylvania

Explore further: Molecular machine, not assembly line, assembles microtubules

Related Stories

Molecular machine, not assembly line, assembles microtubules

August 20, 2015

When they think about how cells put together the molecules that make life work, biologists have tended to think of assembly lines: Add A to B, tack on C, and so on. But the reality might be more like a molecular version of ...

Revealing the inner workings of a molecular motor

January 12, 2015

In research published in the Journal of Cell Biology, scientists from the RIKEN Brain Science Institute in Japan have made important steps toward understanding how dynein—a "molecular motor"—walks along tube-like structures ...

Friction harnessed by proteins helps organize cell division

April 16, 2014

(Phys.org) —A football-shaped structure, known as the mitotic spindle, makes cell division possible for many living things. This piece of cellular architecture, responsible for dividing up genetic material, is in constant ...

Experiments show hypothesis of microtubule steering accurate

January 23, 2014

Tiny protein motors in cells can steer microtubules in the right direction through branching nerve cell structures, according to Penn State researchers who used laboratory experiments to test a model of how these cellular ...

Molecular motors” involved in chromosome transport observed

November 26, 2013

Researchers at Waseda University in Japan have for the first time directly observed the "molecular motor", called Xkid, that plays a critical role in facilitating the proper alignment of chromosomes during cell division. ...

Recommended for you

New Horizons team selects potential Kuiper Belt flyby target

August 29, 2015

NASA has selected the potential next destination for the New Horizons mission to visit after its historic July 14 flyby of the Pluto system. The destination is a small Kuiper Belt object (KBO) known as 2014 MU69 that orbits ...

Interactive tool lifts veil on the cost of nuclear energy

August 24, 2015

Despite the ever-changing landscape of energy economics, subject to the influence of new technologies and geopolitics, a new tool promises to root discussions about the cost of nuclear energy in hard evidence rather than ...

0 comments

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.