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Darwin's beautiful machines

23 September 2009

Sir Charles Darwin
Sir Charles Darwin

An international team of researchers, including Monash biochemists, has discovered molecular level evidence that supports one of the key tenets of Darwin's theory of evolution.

Professor Trevor Lithgow said the breakthrough, funded by the Australian Research Council and published recently in the prestigious journal PNAS, provided a blueprint for a general understanding of the evolution of the "machinery" of human cells.

"Our cells, and the cells of all organisms, are composed of molecular machines," Professor Lithgow said.

"These machines are built of component parts, each of which contributes a partial function or structural element to the machine.

"How such sophisticated, multi-component machines could evolve has been somewhat mysterious, and highly controversial."

A non-Darwinian explanation, from believers of Intelligent Design, proposed these machines to be so neatly complex and complete that they couldn't have evolved but rather must have been designed by an intelligent entity.

"Simple 'core' machines were established in the first eukaryotes (organisms with complex cells) by drawing on pre-existing proteins that had previously provided distinct, simplistic functions" Professor Lithgow said.

The research focused on one specific molecular machine, the TIM complex, which transports proteins into mitochondria - a compartment of human cells that serve as the energy-producing "powerhouses". At a very early stage in evolution, mitochondria were derived from bacteria that lived within the first eukaryotic cells.

The group looked at the bacterium Caulobacter crescentus and found bacterial proteins related to the components of the mitochondrial TIM complex.

"Francois Jacob described evolution as a tinkerer, cobbling together proteins of one function to yield more complex machines capable of new functions," Professor Lithgow said.

"Our work describes a perfect example of Jacob's proposition, and shows that Darwin's theory of evolution beautifully explains how molecular machines came to be."

Professor Lithgow was joined by Monash researchers Dr Abigail Clements, Dr Dejan Bursac, Dr Xenia Gatsos, Dr Andrew Perry, Srgjan Civciristov and Nermin Celik and researchers from the University of Melbourne and Yale University.