Scientists claim to have found evidence at the molecular level in support of one of the key tenets of naturalist Charles Darwin’s theory of evolution.
People have long argued that the molecular machinery of cell is too complex to have evolved, but an international team, led by Monash University, has now come up with evidence to support Darwin’s theory.
Team leader Prof Trevor Lithgow said the breakthrough provided a blueprint for a general understanding of evolution of the “machinery” of our cells, the ‘PNAS’ journal reported.
“Our cells, and the cells of all organisms, are composed of molecular machines. 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.
“Our research shows that these machines although complete and complex, were a result of evolution. Simple ’core’ machines were established in the first eukaryotes by drawing on pre-existing proteins that had previously provided distinct, simplistic functions.
“They therefore stand as proof that Darwin’s theory of evolution breaks down at the molecular level,” he said.
As a model system, the research focussed on one specific molecular machine, the TIM complex, which transports proteins into mitochondria. Mitochondria are 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.
“Our cells literally are chimeras of a ‘host’ cell and these intracellular bacteria. Yet bacteria don’t have TIM complexes - to understand where the TIM complex came from we simply applied scientific reasoning and looked at a modern-day bacterium akin to the organism that gave rise to mitochondria,” Prof Lithgow said.
The group looked at bacterium Caulobacter crescentus and found bacterial proteins related to the components of the mitochondrial TIM complex. They showed that these bacterial proteins are not found as part of protein transport machines.