Intelligent design mavens once cited flagella as evidence of their theory. Scientific fact dispelled that illusion. The mitochondria study does the same for protein transport.
“This analysis of protein transport provides a blueprint for the evolution of cellular machinery in general,” write the researchers, led by molecular biologist Trevor Lithgow at Australia’s Monash University. “The complexity of these machines is not irreducible.”
When they analyzed the genomes of proteobacteria, the family that spawned the ancestors of mitochondria, Lithgow’s team found two of the protein parts used in mitochondria to make TIM23.
The parts are located on bacterial cell membranes, making them ideally positioned for TIM23’s eventual protein-delivering role. Only one other part, a molecule called LivH, would make a rudimentary protein-transporting machine — and LivH is commonly found in proteobacteria.
The process by which parts accumulate until they’re ready to snap together is called preadaptation. It’s a form of “neutral evolution,” in which the buildup of the parts provides no immediate advantage or disadvantage. Neutral evolution falls outside the descriptions of Charles Darwin. But once the pieces gather, mutation and natural selection can take care of the rest, ultimately resulting in the now-complex form of TIM23.
“It hasn’t been possible up until this point to trace any of those proteins back to a bacterial ancestor,” said Dalhousie University cell biologist Michael Gray, one of the researchers who originally described the origins of mitochondria, but was not involved in the new study. “These three proteins don’t perform precisely the same function in proteobacteria, but with a simple mutation could be transformed into a simple protein transport machine that could start the whole thing off.”
“You look at cellular machines and say, why on earth would biology do anything like this? It’s too bizarre,” he said. “But when you think about it in a neutral evolutionary fashion, in which these machineries emerge before there’s a need for them, then it makes sense.”
I think the quote mining was a nice touch, subtle and not too obvious
