In early evolution, the duplication of genes is an important event that resulted in new genes and genetically novel organisms.  For instance, a small soluble iron-sulfur protein known as ferredoxin is found in both modern and ancient entities. Indeed, this commonplace molecule is responsible for mediating electron transfer in a range of metabolic reactions.

Ancient protein fuels modern cells

Now, a study led by researchers at Rice University reverse-engineers a synthetic primordial ferredoxin protein and inserts it into a living bacteria. Accordingly, it successfully powered the cell’s metabolism, growth, and reproduction. The team states their results come closer to understanding how life arose on earth. Similarly, these results open a window on 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 sulfur. Therefore, the earliest cells incorporated these elements into small peptides. Consequently, these became the first basic ferredoxins, proteins which transport electrons within the cell to support metabolism.

Subsequently, as cells evolved, ferredoxins mutated via gene duplication into more complex forms. Presently, ferredoxins derived from this simple ancestor are found in modern bacteria, plant, and animal cells. The current study investigates the theoretical primordial gene duplication origins of bacterial ferredoxins, through a series of synthetic constructs.

The current study compares ferredoxin molecules present in living things to design ancestral forms hypothesized to exist at an earlier stage in the evolution of life. Next, the genome of the bacteria E. coli was minimized to remove the gene it uses to produce ferredoxins.

Finally, an artificial gene encoding for the simpler version of the protein was implanted into the E.coli. Results show different variations of the primordial ferredoxin protein bound two iron-sulfur clusters and were able to support electron transfer in vivo in E. coli.

Ancient proteins can sustain life

The team states live E. coli colonies grew more slowly than usual with the ancient synthetic proteins functioning well enough to transfer electrons between molecules. They go on to add the ferredoxins appearing in modern life are complex, however, a stripped-down version has been engineered still capable of supporting life. Hence, there is potential to build on this simple version for possible industrial applications.

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

Source: Rutgers University 

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