BY AFSHAN NABI (MBG/III)
afshan.nabi@ug.bilkent.edu.tr
A thousand longings such
that over each longing I die (or breathe)
Many of my hopes were fulfilled – and
yet, few were fulfilled
– Ghalib
Another summer of our lives has come to an end. With any luck, your days were filled with peace and warm soaks in the sun. But now, there is some intense living to be done – a new academic year, full of exciting work and pleasing non-work moments beckons.
Hope envelops beginnings like ivy clutches at walls. And because humans are hopeful creatures, you, like me, might have made a bunch of new resolutions for this semester.
It feels good to have goals, to sail on choppy waters while trying to achieve them, in the hope that some day you can look back and find you have fulfilled a dream you had.
But despite the good intentions, you find yourself caught up in the current of the semester, lost in waves of deadlines and trapped under other engagements. And one day, you wake up to realize that you have completely forfeited your personal goals.
But this time, seriously, this time, we can find a way to kick our bad habits in their lousy backsides, right over the deck of the ship into the salty waters, and fervently hope that some nightmarish monsters of the deep devour them. Then, we are going to take over the ship’s wheel and steer it in the direction of our dreams.
Anyway, since I am trying to pass as a geeky biologist these days, I feel obliged to conjure up an inspirational biological metaphor for life here.
Thankfully, biology, unlike myself, rarely lets anyone down, because it is just that incredible. (Engineers, physicists and mathematicians may pride themselves on more rigorous studies, but frankly, biology is so vast, so astounding and so much more fun that a lot of them drop everything and dash off to study biological systems.)
As I was saying, I will present a cool biology phenomenon to inspire all us indolent biological beings to give up our distracted lifestyles of excess food, social media, entertainment, etc., and work on something personally meaningful.
Ladies and gentlemen, consider our underwater “city,” where all forms float around in the water, vibrating relentlessly, like demented buzzing magnets. Consider also that this city is constantly battling against the dark side of the force – entropy. You are a protein fresh out of the production line, with no idea of where you are meant to be. Other proteins and RNA vibrate along, often bumping into you and passing by with a smiling “Sorry mate,” or a threatening “Watch where you’re going, or I’ll unfold you right here.” It is extremely overcrowded. Think of trying to walk around in Taksim, only the road is not straight but branches off in all directions, and in addition to normal people, there are also giants, dwarves and kittens walking the streets. Not only that; any of the passers-by might be carrying large magnets, just as you are carrying some, which attract them to you. Imagine trying to walk with a giant and a kitten sticking to you! Just looking at the crowds and thinking of the physical contact you might be lured into is giving you a headache. Welcome to the Cell!
You are beginning to lose hope that you will ever get out of this city, when (very conveniently, just like in the movies) kinesin, the guy with exactly the right skills to help you, finds you. Kinesin is a molecular motor – it converts chemical energy into mechanical energy and uses that to transport things inside the cell. This is not an easy job considering all the hustle-bustle going on, the constant bumping, bonding and vibration of the molecules in the cell. By human standards, kinesin is a funny-looking thing. It has a long, thin body made of amino acid chains that coil around each other, like a braid. There are hinges in the middle that allow it to bend. At one end, it has two “hands” that contain pockets into which fuel (ATP) can be placed. Breaking down the chemical energy in ATP allows it to stick itself firmly onto the road (fancily called a “microtubule”) and swagger down it, putting one hand in front of another. At the other end, it has a tail that allows it to bind the cargo (that’s you, in this case).
Good-naturedly, the kinesin grabs hold of you. (Maybe another protein saw your helplessness and directed a kinesin to you, or maybe you have a lovely protein pocket that the kinesin takes a fancy to and binds.) In any case, next thing you know, the kinesin is holding onto you, leading you along a microtubule highway. You marvel as you watch other microtubules leading into the depths of the cell, stretching out above, below and beside you. You pass other kinesins carrying other cargo. Just as you begin to feel relieved that you found a kinesin to transport you, you find other traps waiting to ensnare you: traffic jams that may cause the kinesin to get stuck, bigger molecules trying to derail your kinesin off the microtubule, other desperate molecules looking for a lift and trying to entice your kinesin away. Molecules not attached to kinesins bump into you, and you are vibrating (because you are a molecule), but thankfully, the kinesin, which is also vibrating, does not let go. (Or maybe it does, leaving your sorry alpha helices stranded until some other kinesin comes to pick you up.)
Since you are reading this and so also have awareness of the hundred-million-magnitudes-of-length-greater plane of existence where humans live, you can compare hitching a ride on a kinesin to driving in a car. The kinesin, you find, is almost thrice as fast as a car; it covers 360,000 times its length per second, while a car covers only 120,000 times its length. Since a kinesin can convert 60 percent of its energy into useful work, it is also more energy efficient than a car. (Energy efficiency figures for cars seem to range from 10 to 30 percent). But that is not all; it can transport cellular organelles like mitochondria, which, at nearly 4 micrometers, are 400 times its size. That does not sound so impressive until you realize that it is nearly equivalent, lengthwise, to a human being hauling around the Titanic or 12 blue whales.
You are thinking all this while the kinesin trudges on, putting one vibrating foot in front of the other, making decisions about which roads to choose to lead to your destination (not all roads are created equal). At your destination, you hop off, perhaps with the help of yet another protein. As you leave, you turn back to see the kinesin (yawn widely and) fold back on itself using its hinges, bringing its tail to its head to cover the ATP pocket and the head. This is going to prevent ATP binding and waste of energy while it has no cargo to transport, you think, smiling to yourself at the cleverness of this little rescuer of those stranded in a cell.
Many of the mysteries of kinesin (and the cell) remain hidden, but there is no need to panic; fearless biologists continue to tackle these. Meanwhile, I hope this little tale gives you some comfort in cold moments when you feel your grip on your dreams slipping. Be like the kinesin; hold on to your microtubules and your cargo. If you slip, try not to beat yourself up; you will find a way back onto the track.
Have a great week and a productive semester!