Plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. Involved in paracellular magnesium reabsorption. Required for a selective paracellular conductance. May form, alone or in partnership with other constituents, an intercellular pore permitting paracellular passage of magnesium and calcium ions down their electrochemical gradients. Alternatively, it could be a sensor of magnesium concentration that could alter paracellular permeability mediated by other factors (By similarity). Expressed preferentially in kidney. Defects in CLDN16 are a cause of an autosomal recessive chronic interstitial nephritis with diffuse zonal fibrosis (CINF). CINF is characterized by increased blood urea nitrogen, creatinine, and urinary proteins, leads to lethality before puberty, usually within the first 6 months or year of life. Belongs to the claudin family.