2D39

Trivalent Recognition Unit of Innate Immunity System; Crystal Structure of human M-ficolin Fibrinogen-like Domain

Summary for 2D39

• Entry DOI: 10.2210/pdb2d39/pdb
• Descriptor: Ficolin-1, CALCIUM ION (3 entities in total)
• Functional Keywords: innate immunity system, ficolin, m-ficolin, lectin pathway, immune system
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: O00602
• Total number of polymer chains: 3
• Total formula weight: 80674.07

Authors

Tanio, M.,Kondo, S.,Sugio, S.,Kohno, T. (deposition date: 2005-09-26, release date: 2006-12-12, Last modification date: 2024-10-30)

Primary citation

Tanio, M.,Kondo, S.,Sugio, S.,Kohno, T.
Trivalent recognition unit of innate immunity system; crystal structure of trimeric human m-ficolin fibrinogen-like domain
J.Biol.Chem., 282:3889-3895, 2007

PubMed Abstract: Ficolins are a kind of pathogen-recognition molecule in the innate immune systems. To investigate the discrimination mechanism between self and non-self by ficolins, we determined the crystal structure of the human M-ficolin fibrinogen-like domain (FD1), which is the ligand-binding domain, at 1.9A resolution. Although the FD1 monomer shares a common fold with the fibrinogen gamma fragment and tachylectin-5A, the Asp-282-Cys-283 peptide bond, which is the predicted ligand-binding site on the C-terminal P domain, is a normal trans bond, unlike the cases of the other two proteins. The trimeric formation of FD1 results in the separation of the three P domains, and the spatial arrangement of the three predicted ligand-binding sites on the trimer is very similar to that of the trimeric collectin, indicating that such an arrangement is generally required for pathogen-recognition. The ligand binding study of FD1 in solution indicated that the recombinant protein binds to N-acetyl-d-glucosamine and the peptide Gly-Pro-Arg-Pro and suggested that the ligand-binding region exhibits a conformational equilibrium involving cis-trans isomerization of the Asp-282-Cys-283 peptide bond. The crystal structure and the ligand binding study of FD1 provide an insight of the self- and non-self discrimination mechanism by ficolins.

PubMed: 17148457
DOI: 10.1074/jbc.M608627200

Experimental method

X-RAY DIFFRACTION (1.9 Å)