Hin recombinase-DNA complex. Molecular model of the Hin recombinase protein (pink) bound to a double helix (green and orange) strand of DNA (deoxyribonucleic acid). A recombinase is an enzyme that mediates genetic recombination by binding to DNA to form complexes like the one shown here. Only the amino acid binding domain of the Hin recombinase is shown here. This domain is a three-alpha-helix bundle with the carboxyl-terminal helix inserted into the DNA strand's major groove and polypeptide chains either side binding with bases in the DNA strand's minor groove.