Laminin is a large molecular weight glycoprotein present only in basement membranes in almost every animal tissue. Each laminin is a heterotrimer assembled from α, β and γ chain subunits, secreted and incorporated into cell-associated extracellular matrices. The laminins can self-assemble, bind to other matrix macromolecules, and have unique and shared cell interactions mediated by integrins, dystroglycan, and other receptors. Through these interactions, laminins critically contribute to cell differentiation, shape and movement, maintenance of tissue phenotypes, and promotion of tissue survival [1,2].

The different laminin chains share a 600-residue domain I/II which oligomerizes into a rod-like coiled-coil structure forming the long arm of laminins. The N-terminal short arms consist of rod-like elements (domain III and V) formed by tandem arrays of laminin-type EGF modules (see <PDOC00961>) and several globular domains: domains IV and domain VI (laminin N-terminal) (see <PDOC51117>). All α chains share a unique C-terminal G domain which consists of five laminin G modules (see <PDOC50025>) [3]. Laminin IV domain is also found in the perlecan protein, an integral component of basement membranes, which serves also as an attachment substrate for cells, but it is not found in short laminin chains (α4 or β3). The function of this domain is not yet known.

The domain IV of laminin β chains displays no sequence homology to other laminin IV domains, we thus have developed two profiles. The first one recognized all laminin IV domains except the one found in laminin β chains. We have developed a second profile to recognize this atypical domain IV.