Ornithine->Arginine->Lysine. In one study, a DNA binding protein motif, Helix-hairpin-helix (HhH) was ancestrally reconstructed to two primordial protein forms by replacing all lysine residues with O and R, respectively. This reconstructed primordial ornithine-containing motif (pre-O) formed coacervates with poly-uridylic acid (polyU), albeit not as effectively as the reconstructed primitive arginine-containing motif (pre-R). Pre-O was found to be extremely unstructured and disordered, compared to pre-R. Progressive chemical conversion of ornithine residues to arginine led to an increase in DNA binding and folding of the resultant protein each time after conversion, suggesting an increase in structural conformation. This study is one of the only examples that primitive proteins, such as those containing O, could have been more