ENST: The Molecular Sewing Machine

Here’s the amazing story of a
molecular machine in our cells
that works like a sewing machine.

Our CEH editor has been writing articles for Evolution News for over 12 years. This one by David Coppedge was published anonymously on February 19, 2016.

Is It a “Pumpjack”? An “Unsewing” Machine?
In Search of the Right Metaphor for a New Molecular Wonder
Evolution News & Science Today
February 19, 2016

Never presume that the list of molecular machines in the cell is exhausted by the bacterial flagellum, kinesin, and ATP synthase. Those are just three that we have animated thus far. There are so many thousands of machines in living cells, we don’t stand a chance of running out of examples to talk about. Here’s a new one: the “eukaryotic replicative CMG helicase.” Call it CMG helicase for short (the -ase suffix indicates that it operates on a helix, namely the DNA double helix).

Of the many kinds of helicase enzymes that operate on nucleic acids, this one is important right before cell division, when the cell must replicate all of its genetic code. Since DNA consists of two strands, something needs to break them apart so that spare nucleotides can pair up with each side, producing two strands. That’s the job of CMG helicase. You could also compare it to a sewing machine, but an “unsewing” machine would be more accurate. As it passes by, it unzips the DNA strand with a unique rocking mechanism.

Research from Stony Brook University describes how it works. The authors’ preferred metaphor is a “pumpjack” like those machines that rock up and down as they pump oil out of a well. New close-up images of the helicase showed that it takes on two shapes as it moves down the DNA….

Click here to continue reading.