Localization of basic residues required for receptor binding to the single alpha-helix of the receptor binding domain of human alpha2-macroglobulin.
To better understand the structural basis for the binding of proteinase-transformed human alpha2-macroglobulin (alpha2M) to its receptor, we have used three-dimensional multinuclear NMR spectroscopy to determine the secondary structure of the receptor binding domain (RBD) of human alpha2M. Assignment of the backbone NMR resonances of RBD was made using 13C/15-N and 15N-enriched RBD expressed in Escherichia coli. The secondary structure of RBD was determined using 1H and 13C chemical shift indices and inter- and intrachain nuclear Overhauser enhancements. The secondary structure consists of eight strands in beta-conformation and one alpha-helix, which together comprise 44% of the protein. The beta-strands form three regions of antiparallel beta-sheet. The two lysines previously identified as being critical for receptor binding are located in (Lys1374), and immediately adjacent to (Lys1370) the alpha-helix, which also contains an (Arg1378). Secondary structure predictions of other alpha-macroglobulins show the conservation of this alpha-helix and suggest an important role for this helix and for basic residues within it for receptor binding.
Huang
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W
Department of Biochemistry and Molecular Biology, College of Medicine, University of Illinois at Chicago 60612-4316, USA.
Dolmer
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K
Liao
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Gettins
P G
PG
D000595:Amino Acid Sequence; D001665:Binding Sites; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008239:Lysine; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D011994:Recombinant Proteins; D000511:alpha-Macroglobulins; D008239:Lysine