January 5, 2007 | David F. Coppedge

Are Cellular Motors Related by Evolution?

Just because two things go round and round, does that make them related by common ancestry?  A Japanese team thinks so.  A bacterial flagellum rotates (06/04/2002).  So does ATP synthase, though it is about 10 times smaller (04/30/2004).  Publishing in PNAS,1 these researchers looked for a relationship, and noted that these two motors bear some structural similarities.  Also, the Type III Secretion System (TTSS) seems involved in this evolutionary family.  “These results imply an evolutionary relation between the flagellum and F0F1-ATPsynthase and a similarity in the mechanism between FliI and F1-ATPase despite the apparently different functions of these proteins,” they said.

1Imada, Minamino, Tahara and Namba, “Structural similarity between the flagellar type III ATPase FliI and F1-ATPase subunits,” Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0608090104, published online before print January 3, 2007.

Sad to see these researchers, who do great work on understanding cellular motors, be drawn into the dork side of the farce.  Their argument seems based strictly on structural similarity.  This represents a very weak understanding of homology (05/05/2004) and cannot hold up under scrutiny.
    According to Darwinian theory, each random variation or mutation can only be selected if it has survival value.  In the first place, not all bacteria have flagella or TTSS systems, so the evolutionary need for them seems doubtful.  More importantly, how could you go from a working motor to one ten times larger in a stepwise fashion?  Imagine evolving a dump truck from a motorcycle.  Let’s say that the next generation has a lucky mutation on the way to our goal—a piston ten times larger.  But now it doesn’t fit the cylinder!  The motorcycle is broken, and stops working.  Being useless to the motorcycle, it rapidly finds its way to the junkyard.
    The laws of natural selection are very demanding.  Unless each small step aids survival, it cannot be selected.  (We’re assuming here, too, that you hadn’t yet heard that neo-Darwinism has already been falsified, so none of this matters anyway—see 12/14/2006).  All the parts of the ATP-synthase motor and the flagellar motor are not only necessary, they are fitted together to each other’s specifications.  What’s more, the genetic code also has to assemble all these parts in the right order, in the right location, or they won’t work.  In other words, you can’t get from the motorcycle to the dump truck in a series of chance mutations, nor can you get from ATP synthase to a flagellum, or vice versa.
    For these scientists, therefore, to presume for a moment that the two motors are related just because some parts of the ATP-synthase bear some structural resemblance to the parts of the flagellum, like motorcycle to the dump truck, admitting as they do that they have different functions, is ludicrous.  They must realize this.  They work as close as anyone to the paragon of molecular machines (10/07/2006).  They appreciate their complexity (11/02/2005).  Is this paper their annual pinch of incense to Charlie so that they can keep their jobs?  We need scientists with the courage to tell the truth: complex interacting systems do not arise by chance.

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Categories: Cell Biology

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