Expression and refolding of a high‐affinity receptor binding domain from rat α₁‐macroglobulin

Abstract

A recombinant version of the receptor binding domain of rat at-macroglobulin (RBDv) consisting of residues 1319-1474 has been expressed in E. coil. Competition experiments with USl-labelled methylamine treated human a2-macroglobulin reveal that the th-macroglobulin-RBDv exhibit the same high affinity for the c~2-macroglobulin receptor as the entire 40 kDa light chain from rat a~-macroglobulin. It is therefore concluded, that all determinants for receptor interaction reside in the C-terminal approx. 150 residues of the t~-macroglobulin subunit.

Specific Binding of α-Macroglobulin to Complement-Type Repeat CR4 of the Low-Density Lipoprotein Receptor-Related Protein

“…The rat R 1 M RBD was expressed and refolded as described previously (5), and methylamine-activated human R 2 M was a kind gift from L. Sottrup-Jensen (University of Aarhus).…”

Structure of a rat α1‐macroglobulin receptor‐binding domain dimer

“…for LRP than intact a 2 M~Sottrup-Jensen et al, 1986!. Inclusion of the 15 a 2 M residues amino-terminal to the RBD affords a 5-to 10-fold increase in its affinity for LRP, indicating that bordering residues may affect receptor affinity either by modulating RBD conformation or providing additional binding surfacẽ Holtet et al, 1994;Nielsen et al, 1995!. Three aM orthologs are expressed in rat: a 1 M~tetramer!, a 2 M tetramer!, and a 1 inhibitor 3 monomer~a 1 I 3 !~Eggertsen et al., 1991;Warmegard et al, 1992!. In contrast to the other two proteins, rat a 1 M is present in most tissues and is expressed constitutively in plasma. In this regard, rat a 1 M appears to function as a "housekeeping" macroglobulin while the other two are acute phase proteins.…”