Friction, baby
In hard times, how does a cell quickly search through its own DNA to find the genes that will help it survive? The genomes of even the smallest organisms are enormous, and searching along all of the DNA in a cell to find a single site is a complex challenge if you want to do it in any reasonable amount of time. For a sense of scale: all of the DNA within a single human cell, if you unraveled it and stretched it out in a single strand, would be about as tall as you are! (Now, imagine walking along that strand of DNA with legs that are only a nanometer long…)
A friend Michelangelo D’Agostino recently wrote a review of a French group’s efforts to explain the amazing efficiency with which proteins can slide along DNA strands without falling off or getting stuck somewhere along the strand. It turns out that the proteins take a hovercraft approach: they have evolved to have a strong affinity for DNA, but they have also engineered their interactions with the DNA such that when they bind to it, a layer of water gets excluded between the protein and DNA.
Water molecules in the vicinity attempt to diffuse into this region, and the pressure they put between the protein and DNA wedges them just far enough apart that the protein essentially floats on the DNA. The protein can then slide freely along the DNA with minimal friction while it searches for the DNA sequence that it targets.
This is intriguing because their model is surprisingly simple: the DNA and protein were modeled as very basic shapes, but they managed to extract this behavior in an elegant and compelling way.
(To clarify the title of this post: it’s a quote from the Rolling Stones about how they stayed together for so long.)