Peroxins (or peroxisomal/peroxisome biogenesis factors) represent several protein families found in peroxisomes. Deficiencies are associated with several peroxisomal disorders. Peroxins serve several functions including the recognition of cytoplasmic proteins that contain peroxisomal targeting signals (PTS) that tag them for transport by peroxisomal proteins to the peroxisome. Peroxins are structurally diverse and have been classified to different protein families. Some of them were predicted to be single-pass transmembrane proteins, for example Peroxisomal biogenesis factor 11.