Allocation of EMS-induced LanB1 mutations. (A) Domain organization of Drosophila Laminin B1 and location of the isolated mutations. The affected amino acid positions with the corresponding change are given below the allele number (* = stop). The described hypomorphic LanB1 mutations (yellow) all cluster within the Laminin N (LN) domain. (B) Schematic of the laminin α/β/γ trimer illustrating the location of the β laminin domains using the color-coding shown in A. (C) Alignment of the C-terminal part of the LN domain from Drosophila melanogaster LanB1 (D.m., GenBank AAF52563) with that of β laminins Lamb1 and Lamb2 of mouse (M.m., AAI50810.1, AAC53535.1) and human (H.s., AAA59482.1, AAB34682.2). Red letters indicate 100% identity. Secondary structure elements below are according to the structure model shown in D. (D) 3D-structure of mouse Laminin β1 LN-LE1 (4AQS, , illustrated using the Protein Workshop tool ). The LN domain (blue/green) and the closely linked first EGF-like (LE) domain (red) are depicted from two angles. The amino acid residues that correspond to those affected in the hypomorphic LanB1 alleles (highlighted in yellow) are situated on the same side of the β-sandwich structure.