Structure of 450 million year old protein reveals evoluti...(otein via a large database of modern rec...)

Only seven mutations were needed to bridge the 450-million-year gulf, the researchers found. However, not every mutation changed the proteins function. These permissive mutations appear to pave the way for future, more significant changes. Its like they prepared for opportunity to knock in the form of a new hormone, Ortlund said.

The permissive mutations bolstered the receptors structure, like contractors reinforce a historic homes foundation before making renovations. After these changes took place, a more extreme mutation repositioned an entire group of atoms, bringing them closer to fitting the cortisol hormone. Another created the tight new fit with cortisol.

These permissive mutations are chance events. If they hadnt happened first, then the path to the new function could have become an evolutionary road not taken, said co-author John Thornton, a professor of evolutionary biology at the University of Oregon.

The researchers worked out which mutations came first by synthesizing different versions of the mutated protein in the laboratory. Had the radical mutations come first, the receptor protein would have lost its function entirely, they found.

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