Trimeric structure and conformational equilibrium of M-ficolin fibrinogen-like domain.
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 A resolution, and compared with that of the human fibrinogen gamma 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 pK(a) values of His284 are 6.1 and 6.3 in the active and non-active forms, respectively.
Tanio
Michikazu
M
Mitsubishi Kagaku Institute of Life Sciences (MITILS), 11 Minamiooya, Machida, Tokyo 194-8511, Japan.
Kondo
Shin
S
Sugio
Shigetoshi
S
Kohno
Toshiyuki
T
D001704:Biopolymers / Q000737:chemistry*; D005340:Fibrinogen / Q000737:chemistry*; D037102:Lectins / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D000097604:Ficolins
D001704:Biopolymers; D005340:Fibrinogen; D037102:Lectins; D000097604:Ficolins