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Publication Abstract from PubMed

The heterotrimeric laminins are a defining component of basement membranes and essential for tissue formation and function in all animals. The three short arms of the cross-shaped laminin molecule are composed of one chain each and their tips mediate the formation of a polymeric network. The structural basis for laminin polymerisation is unknown. We have determined crystal structures of the short-arm tips of the mouse laminin beta1 and gamma1 chains, which are grossly similar to the previously determined structure of the corresponding alpha5 chain region. The short-arm tips consist of a laminin N-terminal (LN) domain that is attached like the head of a flower to a rod-like stem formed by tandem laminin-type epidermal growth factor-like (LE) domains. The LN domain is a beta-sandwich with elaborate loop regions that differ between chains. The gamma1 LN domain uniquely contains a calcium binding site. The LE domains have little regular structure and are stabilised by cysteines that are disulphide-linked 1-3, 2-4, 5-6 and 7-8 in all chains. The LN surface is not conserved across the alpha, beta and gamma chains, but within each chain subfamily there is a striking concentration of conserved residues on one face of the beta-sandwich, while the opposite face invariably is shielded by glycans. We propose that the extensive conserved patches on the beta and gamma LN domains mediate the binding of these two chains to each other, and that the alpha chain LN domain subsequently binds to the composite beta-gamma surface. Mutations in the laminin beta2 LN domain causing Pierson syndrome are likely to impair the folding of the beta2 chain or its ability to form network interactions.

Crystal Structures of the Network-Forming Short-Arm Tips of the Laminin beta1 and gamma1 Chains.,Carafoli F, Hussain SA, Hohenester E PLoS One. 2012;7(7):e42473. Epub 2012 Jul 31. PMID:22860131^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.