NMR solution structure of complement-like repeat CR3 from the low density lipoprotein receptor-related protein. Evidence for specific binding to the receptor binding domain of human alpha(2)-macroglobulin.
We have used NMR methods to determine the structure of the calcium complex of complement-like repeat 3 (CR3) from the low density lipoprotein receptor-related protein (LRP) and to examine its specific interaction with the receptor binding domain of human alpha(2)-macroglobulin. CR3 is one of eight related repeats that constitute a major ligand binding region of LRP. The structure is very similar in overall fold to homologous complement-like repeat CR8 from LRP and complement-like repeats LB1, LB2, and LB5 from the low density lipoprotein receptor and contains a short two-strand antiparallel beta-sheet, a one turn alpha-helix, and a high affinity calcium site with coordination from four carboxyls and two backbone carbonyls. The surface electrostatics and topography are, however, quite distinct from each of these other repeats. Two-dimensional (1)H,(15)N-heteronuclear single quantum coherence spectra provide evidence for a specific, though relatively weak (K(d) approximately 140 microM), interaction between CR3 and human alpha2-macroglobulin receptor binding domain that involves a contiguous patch of surface residues in the central region of CR3. This specific interaction is consistent with a mode of LRP binding to ligands that uses contributions from more than one domain to generate a wide array of different binding sites, each with overall high affinity.
Dolmer
K
K
Department of Biochemistry, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612-4316, USA.
Huang
W
W
Gettins
P G
PG
D000595:Amino Acid Sequence; D001665:Binding Sites; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D016177:Macrophage-1 Antigen / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000737:chemistry / Q000378:metabolism
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D016177:Macrophage-1 Antigen; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins