Members of this family are found in many Borrelia species. They are large outer membrane proteins that exhibit porin activity in planar lipid bilayers. The average single-channel conductance predicts a rather large pore diameter of 2.6 nm. The exact number of transmembrane strands is unknown but prediction methods suggest a large number, which is in agreement with the large pore. There is evidence that the C-terminal region may traverse through the channel and be surface-accessible. There are also indications that native Oms66 can elicit potent bactericidal activity and significant protective immunity against host-adapted organisms.