The primary structure of the SUI1 protein is made up of 108 amino acids. The protein domain has a structure made of a seven-bladed beta-propeller and it also contains a C-terminal alpha helix. Homologues of SUI1 have been found  in mammals, insects and plants. SUI1 is also evolutionary related to proteins from Escherichia coli (yciH), Haemophilus influenzae (HI1225) and Methanococcus vannielii.