DISULFIDE-BONDING BETWEEN DROSOPHILA LAMININ BETA-CHAIN AND GAMMA-CHAIN IS ESSENTIAL FOR ALPHA-CHAIN TO FORM ALPHA-BETA-GAMMA-TRIMER

Assembly of Drosophila laminin alpha, beta and gamma chains was analyz ed by immunoprecipitation of the lysate from metabolically radiolabele d Kc 167 cells with chain-specific antibodies followed by two dimensio nal electrophoresis in which nonreducing and reducing SDS gel electrop horesis are combined, Precipitation of monomeric beta (or gamma) with anti-gamma (or -beta) antibody revealed that beta and gamma form stabl e dimer before they are disulfide-bonded to each other. In contrast, a lpha associates with neither monomeric beta, monomeric gamma nor beta gamma dimer without disulfide-bonding but only with disulfide-bonded b eta gamma dimer to form alpha beta gamma trimers. These results thus d emonstrated that the interchain disulfide-boding between beta and gamm a is essential for alpha to form alpha beta gamma trimer, We also foun d that the alpha beta gamma trimer can be secreted with alpha chain ei ther disulfide-bonded or not bended to the disulfide-bonded beta gamma dimer. (C) 1997 Federation of European Biochemical Societies.