2d39

From Proteopedia

Revision as of 14:22, 20 March 2008

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

Overview

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.

About this Structure

2D39 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Trivalent recognition unit of innate immunity system: crystal structure of trimeric human M-ficolin fibrinogen-like domain., Tanio M, Kondo S, Sugio S, Kohno T, J Biol Chem. 2007 Feb 9;282(6):3889-95. Epub 2006 Dec 4. PMID:17148457

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