A nano-gear in a nano-motor inside you

January 17, 2013, Tata Institute of Fundamental Research
A phagosome transported inside a living cell by molecular motors is held by a laser trap. This allows measurement of the picoNewton forces exerted by motors as they haul the phagosome inside the cell. Credit: Sukant Saran, TIFR

Diverse cellular processes require many tiny force-generating motor proteins to work in a team. Paradoxically, nature often chooses the weak and inefficient dynein motor to generate large persistent forces inside cells. Here we show that a reason for this choice may be dynein's special ability to speed up or slow down depending on the load it senses.

To live is to move. You strike to swat that irritable mosquito, which skilfully evades the hand of death. How did that happen? Who moved your hand, and what saved the mosquito? Enter the Molecular Motors, nanoscale protein-machines in the muscles of your hand and wings of the mosquito. You need these motors to swat , blink your eyes, walk, eat, drink... just name it. Millions of motors tug as a team within your muscles, and you swat the mosquito. This is teamwork at its exquisite best.

Paradoxically, a weak and inefficient motor (called dynein) is the one that generates large forces in many different . Why has nature made this counter-intuitive choice? Scientists at TIFR, led by Dr. Roop Mallik, have discovered that a team of dyneins is able to share a load much larger than any one of them can handle, due to the unique ability of each dynein to change gears. Because of this, dynein's do much better at teamwork than other stronger motors that cannot change gears. This work will be published in the top-tier journal Cell in January 2013.

This is the PhD thesis work of Arpan Rai, who was ably supported by members of Mallik's team, Ashim Rai, Avin Ramaiya and Rupam Jha. This group of young students took a and focused it down to a tiny spot inside a mouse cell. Small objects inside the cell which were being moved around by motors could be trapped in this laser beam. Now, the motors tried their best to pull this object out of this "laser trap". The figure shows an artist's rendition of such an object being pulled out of the laser trap by four dynein motors. Mallik says: "Each dynein showed a special ability to shift gears, just like you shift gears in your car to go uphill. Therefore, each dynein in a team could speed up or slow down, depending how hard it was pulled back. This allowed the dyneins to bunch close together as they were pulling. The bunching helped dyneins to share their load equitably, and therefore work efficiently to generate large forces. Remarkably, motor-teams made up of another motor (called kinesin) which is much stronger than dynein, could not generate comparable forces. The reason? Well … you guessed it right. Kinesin does not have a gear!!"

Taken together, these new studies show that Nature may have learnt how to use the gear in a motor much before we made our Ferrari's and Lamborghini's. But, what boggles the mind is that dynein's gear works on a size scale that is ten-million times smaller than the Ferrari's gear.

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1 / 5 (7) Jan 17, 2013
Why has nature made this counter-intuitive choice

Is nature "alive" that it can make choices?
that Nature may have learnt how to use the gear in a motor much before we made our Ferrari's and Lamborghini's.

Someone once said that it would be impossible to find wheels and motors in biological systems. So just how is it that we DO find them - by the trillions?
At the nano-scale level that these motors work, the thermo-dynamic and chemical forces are so large that it would be stupendously miraculous if these motors could somehow arise from random physical processes. Given the complexity inherent in them, together with their required environments without which they could NOT survive, specific design is a far better explanation for what we encounter.
There has never, ever been a demonstration that such complexity can arise from just random chemical and physical activity.
To assume that it did begs the question.

5 / 5 (5) Jan 17, 2013
Is nature "alive" that it can make choices?

No. Nature evolves to the point of 'good enough'. If photosynthesis in a plant is inefficient - but 1% more efficient than in the next plant, then that is good enough.

So just how is it that we DO find them - by the trillions?

Don't be obtuse. Wheels and motors like we do on a car - not in a metaphorical sense.

miraculous if these motors could somehow arise from random physical processes.

As noted above. If it works (even badly) and the other guys' doesn't work - then you win ni evolution. That is why an eye didn't need to evolv to the quality it has today. IN the early days having something that could just distinguish light from dark was a huge advantag. next you get something that can distinguish large blobs from small blobs, etc, etc - until you end up with something liken aeagle's eye.
To assume that it did begs the question.[/q[
Yep. How you ever survived with lack of brain certainly does. Must be design.

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