Present in the thicker 16-17 nm junctions of mammalian lens fiber cells, where it may contribute to cell junctional organization. Acts as a receptor for calmodulin. May play an important role in both lens development and cataractogenesis. Seems to be associated with itself or another lens membrane component via disulfide bonds. Eye lens specific. The disease is caused by variants affecting the gene represented in this entry. Belongs to the PMP-22/EMP/MP20 family.