Expression of a functional α‐macroglobulin receptor binding domain in Escherichia coli

Abstract

We have expressed receptor-binding domains of human α₂-macroglobulin in Escherichia coli. Expression levels of both recombinants were quite high, but the human one was insoluble, probably forming inclusion bodies. The rat domain, which lacks the human disulfide, was produced in a soluble form and readily purified by two simple chromatographic steps. Purified recombinant rat α₁-macroglobulin receptor-binding domain was fully functional in binding to the α-macroglobulin receptor on human fibroblasts. This 142 residue domain should serve as an excellent template for analyzing the structural requirements for α-macroglobulin receptor ligation and dissecting the varied biological functions resulting from such ligation.