Structural component of lens fiber gap junctions (PubMed:8088962). Gap junctions are dodecameric channels that connect the cytoplasm of adjoining cells. They are formed by the docking of two hexameric hemichannels, one from each cell membrane (By similarity). Small molecules and ions diffuse from one cell to a neighboring cell via the central pore (PubMed:8088962). A hemichannel or connexon is composed of a hexamer of connexins. A functional gap junction is formed by the apposition of two hemichannels (By similarity). Forms heteromeric channels with GJA8 (By similarity). Only detected in the lens. Higher expression in pre-natal (1-5 months gestation) than in postnatal (4-6 months) calf lens. Phosphorylated on multiple threonine and serine residues. Phosphorylation may have a role in assembling connexins into connexons and gap junctional plaques, as well as channel gating. Belongs to the connexin family. Alpha-type (group II) subfamily.