Laminins are the major noncollagenous components of basement membranesthat mediate cell adhesion, growth migration, and differentiation. They arecomposed of distinct but related alpha, beta and gamma chains. The threechains form a cross-shaped molecule that consist of a long arm and three shortglobular arms. The long arm consist of a coiled coil structure contributed byall three chains and cross-linked by interchain disulphide bonds.Beside different types of globular domains each subunit contains, in its firsthalf, consecutive repeats of about 60 amino acids in length that include eightconserved cysteines. The tertiary structure of this domain isremotely similar in its N-terminal to that of the EGF-like module (see <db_xref db="PROSITEDOC" dbkey="PDOC00021"/>). It is known as a 'LE' or 'laminin-type EGF-like' domain. Thenumber of copies of the LE domain in the different forms of laminins is highlyvariable; from 3 up to 22 copies have been found.A schematic representation of the topology of the four disulphide bonds inthe LE domain is shown below. +-------------------+ +-|-----------+ | +--------+ +-----------------+ | | | | | | | | xxCxCxxxxxxxxxxxCxxxxxxxCxxCxxxxxGxxCxxCxxgaagxxxxxxxxxxxCxx sssssssssssssssssssssssssssssssssss'C': conserved cysteine involved in a disulphide bond'a': conserved aromatic residue'G': conserved glycine (lower case = less conserved)'s': region similar to the EGF-like domainIn mouse laminin gamma-1 chain, the seventh LE domain has been shown to be theonly one that binds with a high affinity to nidogen. The binding-sites arelocated on the surface within the loops C1-C3 and C5-C6. Longconsecutive arrays of LE domains in laminins form rod-like elements of limitedflexibility, which determine the spacing in the formation of lamininnetworks of basement membranes.