Hin recombinase is a 21kD protein composed of 198 amino acids that is found in the bacteria Salmonella.
Hin functions to invert a 900 base pair (bp) DNA segment within the salmonella genome that contains a promoter for downstream flagellar genes, fljA and fljB.
Four molecules of Fis bind to this site as a homodimers and are required for the recombination reaction to proceed.
The initial reaction requires binding of Hin and Fis to their respective DNA sequences and assemble into a higher-order nucleoprotein complex with branched plectonemic supercoils with the aid of the DNA bending protein HU.
Activation of the 4 catalytic serine residues within the Hin tetramer make a 2-bp double stranded DNA break and forms a covalent reaction intermediate.