RecA

It functions as a recombinase and strand-exchange protein, catalyzing the central steps of homologous recombination by forming nucleoprotein filaments on single-stranded DNA. Structural and functional homologs to RecA have been found in all kingdoms of life. RecA serves as an archetype for this class of homologous DNA repair proteins. The homologous protein is called RAD51 in eukaryotes and RadA in archaea.

Text adapted from Wikipedia, CC BY-SA 4.0. Photograph: Aristeas and Papias of Aphrodisias (see Commons), Wikimedia Commons.