Protein evolution in the Archean eon

Proteins are the machinery of life, and enzymes are especially critical in directing and accelerating the rate of all biochemical processes. The earliest living form which is tractable, the so-called Last Universal Common Ancestor, LUCA, was already equipped with a large set of fully functional enzymes. As far as phylogenetic analysis can reveal, these LUCA enzymes were essentially identical to their modern descents – namely large and complex proteins. How these evolved from shorter and simpler proteins (or peptides) remains enigmatic. I will describe our efforts to infer the early pre-LUCA precursors, reconstruct and test them in the laboratory, and also what these precursors teach us about the earliest stages of protein evolution.