Posted: Jul 23, 2010 12:40 am
by CharlieM
Well to be honest I don't even think the evolution of the hook poses much of a problem and a possible solution is quite simple.

I would say that the more technology advances and the closer we can look at these things, the less likely that the solution is simple.
When Prof. Namba’s group attached a 40 nm fluorescence bead to the flagellar motor and observed the motor rotation, the group was surprised to see large and rapid fluctuations of the rotation speed. The key to revealing the mystery of the motor must be hidden behind the thermal fluctuation of the protein structure, which is still so far from understanding. “The atoms constituting proteins do fluctuate but the average positions of individual atoms are very precisely determined with an accuracy of sub-angstrom level. That is why individual proteins can properly identify partner molecules to bind and get assembled into the higher order structures of living organisms. The fluctuations of protein structure, that’s what makes living organisms function in such sophisticated and well regulated ways. I am willing to dedicate my entire life to the hard work unveiling the mysterious world of protein structure and function.”

This duplicated rod is straight to begin with and is slowly accumulating mutations making it bend while retaining structure. Remember, these are individual molecules sticking together entirely by intermolecular attraction forces. It is not unreasonable to postulate that this complex can undergo a very slight twist without breaking. And the proto-flagellum was propably quite slowly rotating. What is now left for evolution to do is simply to filther through mutations for improved function over generations. The pro-flagellum before a bent hook as we see it today arrived, was providing motility already, but it was poor at it. But poor is better than none at all.

Poor motility is no use if it is not strong enough to overcome Brownian motion.

Bending a rod does not give you a universal joint. Ask an engineer to make you a mock up of the flagellum with just a bent tube where the hook should be and he'll say. "no problem". But ask him to make one with a universal joint and you'll have him scratching his head.