Walking Heads: Kinesin or The Little Engine That Could :)

Walking Heads: Kinesin or The Little Engine That Could 🙂

Have you wondered how things (like vesicles and mitochondria) move about inside a cell? They don’t just drift aimlessly through the thick cytoplasmic soup-rather they are ferried by kinesin, a hard working molecular motor.

To watch mitochondria motor down an invisible highway inside a nerve cell see: Mitochondrial Moving in an Axon.mov

The kinesin highway is made of microtubules : a bundle of 13 filaments that have distinct ends (known as + and – ends). Kinesins move cargo towards the + end (from the center of the cell to the periphery) and dyneins move them in the opposite direction. Watch what happens when fluorescent microtubules are placed on a slide coated with kinesin! Kinesin-1 gliding motility assay, whole casein passivation.avi

Cargo is tethered to kinesin by a long coil. The two heads of the motor walk along the microtubule in a hand-over-hand mechanism using ATP hydrolysis as a power source. Each ATP moves the motor one 8 nanometer step. Notice that kinesin is a processive motor: once it is attached to the microtubule it takes (on average)100 steps, before it lets go.

For a narrated 2 min mechanism see:Kinesin Walking Narrated Version for Garland

Many, many thanks to Kevin Staff for being such a sport and converting the kinesin video into an animated gif! Special shout out to Andreas Schou who requested some ‘kinesin love’ and to Henry K.O. Norman who is working on an animated production on cellular mechanisms.

For #ScienceSunday curated by Allison Sekuler and Robby Bowles .

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53 Responses to Walking Heads: Kinesin or The Little Engine That Could :)

  1. Bailey Roe says:

    I’ve always loved these little guys. The cell can be such an amazing thing.

  2. Kinesins are super cute — their cartoony, stumbling gait is always sort of hilarious, unlike the mechanical efficiency of most other molecular motors.

  3. Rajini Rao says:

    Andreas Schou , myosin motors would look manic by comparison 😉 All rowing away, out of synchrony, but somehow generating an awesome force for muscle contraction.

  4. Rich Pollett says:

    Yay Rajini Rao and you have the gif too. Thanks for the great post and links also!

  5. Rajini Rao says:

    Rich Pollett , I screwed up the courage to ask Kevin Staff and he was so quick that he caught me unprepared without a text to go with it. G+ is a great place for creative collaborations!

  6. Rajini Rao says:

    J Huntemann , LOL, so now I need someone to pick up on the play on Walking Heads!

  7. Rich Pollett says:

    Lot’s of bright talented folks here, sharing such interesting information and as you said the levels of collaborations – amazing. The reason I enjoy G+ so much. 🙂

  8. wonderful animation. Thank you!

  9. Thanks for sharing this, one comment on that YouTube video says: “People should know that this is wrong. It has since been shown that it is not a “power stroke” that makes kinesin move.” Is this accurate?

  10. Rajini Rao says:

    Hi, Andrej Karpathy . All motors have power strokes..that refers to the step that transfers energy from ATP hydrolysis to work that the motor is doing. Here is an excerpt from a paper: “All motor proteins undergo conformational changes and transmit those in such a way that force is exerted on their cargos. When part of the molecule acts as a lever arm, these conformational changes are dubbed power strokes. Processive motors (most often dimeric) alternate power strokes to always maintain contact of one of their monomers to the track and thus perform steps along the track…Nonprocessive motors, such as myosin-2 or ncd, perform a power stroke and then detach from the track.” Hope that makes sense!

    Ref:Biophys J. 2010 December 15; 99(12): 3905–3915.

    doi: 10.1016/j.bpj.2010.10.045

  11. Ok, so basically we don’t know what the YouTube commenter is referring to. thanks.

  12. Rajini Rao says:

    Yes, that was a vague comment. Exactly which step is the power stroke may be under debate and differs between motors, but I’m not sure what the alternative is.

  13. Very well done! Thank-You!

  14. Seth Russell says:

    Great animation! Years ago i went looking for an animated image to illustrate my concept of “Sticky Cyber Molecules” … i never did find one that i liked … well, now i have 🙂


  15. Rajini Rao says:

    Seth Russell 🙂 I look forward to seeing kinesin walking around your web site.

  16. This looks like somebody trying to play QWOP for the first time

  17. Rajini Rao says:

    Steele Parker , I had to ask my 13 yr old son for an explanation, and he concurs with your description 🙂

  18. John T. says:

    Thanks for sharing a post so dense of information

  19. Right must we have think about it as it is out of the box !!

  20. Rajini Rao, sadly, your 13 year old son probably understands molecular biology (is that even the right field?) better than me….

  21. Rajini Rao says:

    Steele Parker , there does not appear to be much molecular biology besides disintegrating bodies on Team Fortress 2, alas! However, I have it on good authority (older males) that younger males do eventually amount to some good, so I live in hope. 🙂

  22. this is one of my projects, myosin/actin.

  23. Rajini Rao says:

    That’s great, Ming-Yuan WEI ! Looking forward to hearing more about myosin motors from you, then 🙂

  24. RJ Matlock says:

    What produces the mircotubule’s and were do it go after being used up ?

  25. Thank you for sharing this. Very interesting!

  26. Thank you so much for writing these posts about the microscopic activities of our bodies. They’re really interesting.

  27. Rajini Rao says:

    RJ Matlock , microtubules are fascinating in their own right! They are polymers, made of monomeric proteins known as tubulin. The polymers are continually forming and falling apart at the two ends, although one end is more stable than the other. In a cell, the stable end arises from the “microtubule organizing center” located near the nucleus. Microtubules have an interesting property called dynamic instability..they can suddenly stop growing and collapse completely into monomers: Dynamic Instability of Microtubules This is useful during cell division when the microtubules “seek” and attach to chromosomes which are then pulled towards the poles of the cell. Here is another animation, showing a built in timer because of GTP breakdown by the monomer tubulin: Microtubule.avi

  28. Wow…Thanks for providing the info to make me think in this area. I do mechanical / robotic programming/assembly and this is out of my field. Always open to learn more so TYVM.

  29. Really knowledgeable!thanks for posting

  30. Very Cool……Wow… look at the response this post is getting…

    You Go Rajini- You are going to set a record!

  31. God I love being a complex organism!

  32. Tom Lee says:

    Nice post Rajini Rao so amazing. It could learn how to do the Tango soon.

  33. Ah, I miss my undergrad…

  34. Watching this video in college made me decide to go into research science. You can watch a free online seminar by Ron Vale (he discovered kinesins) here: http://www.ibioseminars.org/lectures/bio-mechanisms/ron-vale.html and a short talk about how he made his discovery here: http://ibiomagazine.org/index.php/issues/august-issue/molecular-motor-search

  35. Randi Miller says:

    oohhh you science geeks 🙂

  36. Lacy Galtere says:

    Rajini Rao I cannot wait for them to start coming out with more of these animated-type models that actually show what’s happening on the cellular level (and even, at the neuromuscular junction).. will bode well for future presentations :o) they incorporated one of these at a recent presentation at my college; I believe it was the myosin model… Fascinating. Thanks so much for sharing!

  37. John T. says:

    I am amazed to see so much involvement in a scientific post like this! Its encouraging to think that not only cat videos and animals using tablets can go viral

  38. thank you Rajini , good grafiics

  39. Rajini Rao says:

    Sarah Goodwin , thank you for the links! Anyone interested can check out the seminars. The animation I showed is also on Ron Vale’s lab page along with a few other movies: http://valelab.ucsf.edu/

  40. Rickie B says:

    Nice Rajini – very int science – talk soon Rsj

  41. Rajini Rao says:

    Subrata Dutta , thanks..good to see you here on G+!

  42. Knowing a lot from your posts.

  43. Can you describe time scale on which this process happens? I bet it interests a lot of people…

  44. Rajini Rao says:

    Klemen Zhivko , the motor walks in 8 nanometer steps. The velocity depends on the load to which it is attached at the rod shaped end (since the load can be an entire mitochondrion or vesicle, which is huge). If you look at the graph in the link to Stephen Block’s lab page, you will see that the overall velocity of 25 nm/sec in the traces shown, is actually composed of long pauses of random lengths with rapid (microsecond) movements in between. That is why an animation showing the kinesin striding along (like John Travolta in the BeeGee’s Staying Alive song!) is inaccurate. 


  45. Rajini Rao says:

    Kimberly Chapman , awesome 🙂 

    I’m going to comment on your post (when I get a break from work) with an interesting difference between the two animations that I hope Peo will appreciate. Hint: the word is stochastic and it relates to single molecules

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