The best-accounted function MIP-26 in the lens is

Although the proteins of the lens plasma membranes constitute to no more than 1% of the lens wet weight, they are critically impoant for the lens functions including transparency. The lens membrane protein that has perhaps been most highly studied is MIP (for major intrinsic protein), also called MIP26. MIP26 is a lens fiber-specific integral membrane protein, which mediates the passage of small molecules through the membranes. MIP26 does not appear to form an intercellular channel as do the connexons in gap junctions but may form channels to the extracellular space, possibly providing indirect connections or helping to minimize the extracellular space and enhance less transparency. It serves two major functions to maintain the transparency of lens Transpo of water across the lens Transpo of glycerol across the lens