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Localization of the specific binding site for magnesium(II) ions in factor IX
Author(s) -
Sekiya Fujio,
Yoshida Misa,
Yamashita Toshiko,
Morita Takashi
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00813-7
Subject(s) - chemistry , binding site , conformational change , ion , quenching (fluorescence) , fluorescence , peptide , metal ions in aqueous solution , crystallography , binding domain , magnesium , factor x , biophysics , stereochemistry , biochemistry , biology , physics , platelet , organic chemistry , quantum mechanics , immunology , thrombin
We demonstrated recently that coagulation factor IX has a specific binding site(s) for Mg 2+ ions, independent of the Ca 2+ ‐binding sites, and that binding of Mg 2+ ions is very important for expression of the functional conformation of this protein. We report here the localization of this Mg 2+ ‐specific binding site. We prepared three Gla‐containing fragments of bovine factor IX, namely GlaEGF NC (residues 1–144+286–296), GlaEGF N (1–83) and the Gla domain peptide (1–46). Fragments GlaEGF NC and GlaEGF N retained the ability to undergo a conformational change upon binding of Mg 2+ ions in the presence of excess Ca 2+ ions. This change could be detected by a conformation‐specific antibody. Furthermore, the Gla domain peptide was capable of binding Mg 2+ ions, as determined by the metal ion‐induced quenching of the intrinsic fluorescence. It appears that the Mg 2+ ‐specific binding site of factor IX is located in the N‐terminal Gla domain.