Open AccessTrimeric structure and conformational equilibrium of M‐ficolin fibrinogen‐like domain
Author(s) -
Tanio Michikazu,
Kondo Shin,
Sugio Shigetoshi,
Kohno Toshiyuki
Publication year - 2008
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049507054325
Subject(s) - ficolin , chemistry , ligand (biochemistry) , isomerization , active site , peptide , molecule , protein structure , stereochemistry , crystallography , peptide bond , receptor , innate immune system , biochemistry , enzyme , organic chemistry , catalysis
Ficolins are pathogen‐recognition molecules in innate immune systems. The crystal structure of the human M‐ficolin recognition domain (FD1) has been determined at 1.9 Å resolution, and compared with that of the human fibrinogen γ fragment, tachylectin‐5A, L‐ficolin and H‐ficolin. The overall structure of FD1 is similar to that of the other proteins, although the peptide bond between Asp282 and Cys283, which is in a predicted ligand‐binding site, is a normal trans bond, unlike the cases of the other proteins. Analysis of the pH‐dependent ligand‐binding activity of FD1 in solution suggested that a conformational equilibrium between active and non‐active forms in the ligand‐binding region, involving cis‐trans isomerization of the Asp282—Cys283 peptide bond, contributes to the discrimination between self and non‐self, and that the p K a values of His284 are 6.1 and 6.3 in the active and non‐active forms, respectively.