Researchers insert a synthetic primordial protein into a living organism.

Gene duplication is an important event in early evolution which results in new genes and genetically novel organisms.  A classic example is the small soluble protein ferredoxin, an iron–sulphur protein with ancient origins which mediate electron transfer in a range of metabolic reactions. Now, a study led by researchers at Rice University reverse-engineers the primordial ferredoxin protein and inserts it into a living bacteria, where it successfully powered the cell’s metabolism, growth and reproduction. The team state their results come closer to understanding how life arose on earth and the pathways life may have taken on exobiological worlds. The study is published in the journal Proceedings of the National Academy of Sciences.

Previous studies show life on earth may have arisen near hydrothermal vents rich in iron and sulphur. Therefore, the earliest cells incorporated these elements into small peptides, which became the first basic ferredoxins, proteins which transport electrons within the cell to support metabolism. As cells evolved, ferredoxins mutated via gene duplication into more complex forms. The ferredoxins in modern bacteria, plant and animal cells are all derived from that simple ancestor, although this has never been proven in practical terms. The current study investigates the theoretical primordial gene duplication origins of bacterial ferredoxins, by designing a series of synthetic constructs.

The current study compares ferredoxin molecules which are present in living things and, using computer models, designs ancestral forms which may have existed at an earlier stage in the evolution of life. The genome of the bacteria E. coli was minimised to remove the gene it uses to produce ferredoxins, which was then replaced by an artificial gene that encodes for the simpler version of the protein. Results show different variations of the primordial ferredoxin protein bound two iron-sulphur clusters and were able to support electron transfer in vivo in E. coli.

The team state that although the E. coli colonies grew more slowly than usual, they did survive, with the ancient proteins functioning well enough to transfer electrons between molecules. They go on to add that the ferredoxins which appear in modern life are complex, however, a stripped-down version has been engineered that still supports life, with the potential to build on this simple version for possible industrial applications.

The team surmise they have successfully inserted a synthesized, primordial protein into living cells to identify the origins of metabolism. For the future, the researchers state that understanding how metabolism works could allow the global medical community to program microbes for all sorts of uses, such as energy storage, biofuel production or even fighting viruses.

Source: Rutgers University

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