Human Nidogen‑2 Biotinylated Antibody

Nidogen-2 (also named entactin-2) is a 200 kDa, secreted, monomeric basement membrane glycoprotein (1). Nidogens 1 and 2 are expressed in nearly all basement membranes (1‑3) where they interact with laminins, collagen type IV and proteoglycan family members to form structural scaffolds (4, 5). In mouse, Nidogens 1 and 2 appear to substitute for each other. Deletion of one nidogen gives a mild phenotype, but deletion of both nidogens is lethal (6, 7). Affinity of laminin binding is much lower for human Nidogen-2 than that of mouse Nidogen-2, indicating that human Nidogen-2 may not be a strict substitute for Nidogen-1 (1). Both nidogens bind perlecan and collagens I and IV, but only Nidogen-1 binds fibulins (1, 3). The two nidogens show approximately 50% amino acid (aa) identity in human and are structurally similar (1, 4, 6). Cleavage of a 28 aa signal sequence from human Nidogen-2 produces a 1219 aa mature protein containing three globular domains (G1‑3) separated by a link region and an extended rod-shaped segment. The G1 domain is reported to bind type IV collagen, the G2 Nidogen ( beta -barrel) domain interacts with perlecan, and the C-terminal G3 beta -propeller structure is associated with laminin binding. The mucin-like link region is longer in Nidogen-2 than nidogen-1, and contains both N- and O-glycosylation (2, 8). There is one EGF‑like motif and a short peptide that ligates alpha ₃ beta ₁ integrins. The rod-shaped segment contains four additional EGF‑like motifs, two of which bind calcium, and two thyroglobulin type 1 domains that serve as a binding site for alpha _v beta ₃ integrins. Mature human Nidogen-2 is 80% aa identical to both mouse and rat Nidogen-2, and 73% aa identical to both canine and bovine Nidogen-2.