Disulfide‐bonding between <i>Drosophila</i> laminin β and γ chains is essential for α chain to form αβγ trimer

Abstract

Assembly of Drosophila laminin alpha, beta and gamma chains was analyzed by immunoprecipitation of the lysate from metabolically radiolabeled Kc 167 cells with chain-specific antibodies followed by two dimensional electrophoresis in which non-reducing and reducing SDS gel electrophoresis are combined. Precipitation of monomeric beta (or gamma) with anti-gamma (or -beta) antibody revealed that beta and gamma form stable dimer before they are disulfide-bonded to each other. In contrast, alpha associates with neither monomeric beta, monomeric gamma nor betagamma dimer without disulfide-bonding but only with disulfide-bonded betagamma dimer to form alpha betagamma trimers. These results thus demonstrated that the interchain disulfide-boding between beta and gamma is essential for alpha to form alpha betagamma trimer. We also found that the alpha betagamma trimer can be secreted with alpha chain either disulfide-bonded or not bonded to the disulfide-bonded betagamma dimer.