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(Permalink) Posted: Feb. 12 2012,10:41   

Quote (dvunkannon @ Feb. 10 2012,16:15)
http://www.nature.com/nsmb.......41.html

It makes some big claims about helping to explain an RNA World to protein world transition, but it also makes my head hurt.

Anyone want to take a shot at summarizing?

Quick version:

GTPases are enzymes that hydrolyze GTP to GDP. They can act as molecular switches to regulate other processes-usually the GTP-bound state being an "on" signal and following hydrolysis, the GDP-bound state is "off."

The off-to-on and on-to-off states are regulated. Canonical GTPases have a GAP (GTPase activating protein) which generally supply a catalytic residue (amino acid) in trans, which activates hydrolysis, and makes the "off" state.

Some GTPases have all needed catalytic residues built-in. One might conclude they aren't regulated-just timed by their intrinsic activity. This study claims to show another protein binding the GTPase pushes this GTPase's own catalytic residues into position, acting like a GAP, except it gives it a nudge that makes the catalysis more efficient, instead of contributing a catalytic amino acid sidechain.

The authors suggest RNA could play a similar role-in targeting RNA protein complexes in translation--for protein localization, etc. The GTPases that use the new mechanism are ancient and conserved. They suggest RNA as a GAP  predates protein GAPs-perhaps even going back pre-LUCA.

  
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