I just became aware of two new papers that are especially useful during the review of Darwin’s Doubt, because they directly address some issues that Meyer has. But, beyond that, these a freaking cool.
I’m trying to get the full papers, but the abstracts will do (anyone who has a PNAS subscription…).
The first is Biophysical mechanisms for large-effect mutations in the evolution of steroid hormone receptors. In this study the authors take a look at whether small mutations can have major effects. Unsurprisingly, they can.
The authors looked at steroid receptors. These are the proteins that steroids attach to and then generate some effect. A particular one they looked at was an estrogen receptor. In this case, a pair of point mutations resulted in a 70,000 fold change in receptor specificity. Before the mutations, this protein was highly specific for estrogen… and only estrogen. After the mutations, darn near any steroid would work and it was significantly less specific for estrogen.
Here’s the interesting thing though. This isn’t some pipe dream that we wish it work out this way or that, it could work this way if we specifically design it to. This is an ancestral reconstruction. This has already happened and the authors are trying to figure out how.
Turns out, it was bloody simple. Two point mutations and the entire protein basically does something else.
The second article is more complex, not as readily cool, but really interesting to me because I love OOL research. The article is Nucleobases bind to and stabilize aggregates of a prebiotic amphiphile, providing a viable mechanism for the emergence of protocells.
I know, from the title it’s obvious what’s going on and I don’t even have to explain it.*
OK, OK. So one of the questions is how can we make cells out of some material and get the RNA (presumably) into it and keep the whole thing stable in salt water long enough for this to actually be considered a functioning cell.
Turns out (like a lot of things in OOL research), it’s a lot easier than anyone previously thought.
Basically, a prebiotic compound called decanoic acid (and it’s aggregates) will bind to ribose sugars and nucleic acids. Ribonucleic Acid… RNA. What’s even better, when these are bound by the acid, it prevents flocculation, that is, it prevents the sugars and bases from coming out of the solution and just falling to the bottom of the sea.
Curiously, and adding support for the RNA World hypothesis, the inhibition of flocculation is dependant on the degree of binding… and the binding strength with ribose sugars is greater than three similar sugars. Finally, the effects are additive. When a ribose AND a nucleic acid are bond to the acid, the stability is greater than either by themselves.
The presence of this one compound does a lot to stabilize RNA and, according to the authors, may have driven the emergence of protocells.
This is the cutting edge.
____________________________
* I told my wife the title and she just rolled her eyes at me and gave me that “WTF?” look.
