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

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Abstract
Assembly of Drosophila laminin α, β and γ 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 β (or γ) with anti‐γ (or ‐β) antibody revealed that β and γ form stable dimer before they are disulfide‐bonded to each other. In contrast, α associates with neither monomeric β, monomeric γ nor βγ dimer without disulfide‐bonding but only with disulfide‐bonded βγ dimer to form αβγ trimers. These results thus demonstrated that the interchain disulfide‐boding between β and γ is essential for α to form αβγ trimer. We also found that the αβγ trimer can be secreted with α chain either disulfide‐bonded or not bonded to the disulfide‐bonded βγ dimer.