Binding to cells via a high affinity receptor, laminin is thought to mediate the attachment, migration and organization of cells into tissues during embryonic development by interacting with other extracellular matrix components. Laminin-5 is thought to be involved in (1) cell adhesion via integrin alpha-3/beta-1 in focal adhesion and integrin alpha-6/beta-4 in hemidesmosomes, (2) signal transduction via tyrosine phosphorylation of pp125-FAK and p80, (3) differentiation of keratinocytes. Laminin is a complex glycoprotein, consisting of three different polypeptide chains (alpha, beta, gamma), which are bound to each other by disulfide bonds into a cross-shaped molecule comprising one long and three short arms with globules at each end. Alpha-3 is a subunit of laminin-5 (laminin-332 or epiligrin/kalinin/nicein), laminin-6 (laminin-311 or K-laminin) and laminin-7 (laminin-321 or KS-laminin). Major component. Basal membrane of the upper alimentary tract and urinary and nasal epithelia, salivary glands and teeth (both variants). Isoform A is predominantly expressed in skin, hair follicles and developing neurons of the trigeminal ganglion. Isoform B was found in bronchi, alveoli, stomach, intestinal crypts, whisker pads, CNS, telencephalic neuroectoderm, thalamus, Rathke pouch and periventricular subependymal germinal layer. The alpha-helical domains I and II are thought to interact with other laminin chains to form a coiled coil structure. Domains IV and G are globular.