Moselio Schaechter

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September 06, 2010

Talmudic Question #65

What is it about the cyclic nature of nucleotides, both monomers and dimers, that makes them such favorites for signaling purposes?


A good signal molecule must be chemically unstable - easily and spontaneously degraded into non-signal. After all, you don't want your signal receptors to be getting all excited about yesterday's news. Phosphate di-esters are easily hydrolysed. Also, easy to manufacture with enzymes that are just one evolutionary tweak away from existing enzymes.

I'm also interested in why some bacteria have more than one adenylate cyclase like gene. Certainly, in Myxococccus, one cya gene is involved with osmotic sensing...and one presumably for more common metabolic functions. But all of these genes make enzymes that synthesize the same product: cAMP. I can only guess that there must be cAMP receptor proteins with different affinities? Or a localization effect at "one end" of a cell.

And I haven't even started thinking about cycle-di-nucleotides....I need aspirin.

As for the the reason that they are such "good" signaling ligands, well, their commonality with DNA metabolism, and the fact that so many proteins have the ability to recognize nucleic acids and nucleotides some to mind. So the toolboxes might be similar?

Or I may be falling into the chicken-egg quandary....

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