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Calcium binding to the first EGF‐like module of human factor IX in a recombinant fragment containing residues 1–85
Author(s) -
Persson Kristina E.M,
Astermark Jan,
Björk Ingemar,
Stenflo Johan
Publication year - 1998
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/s0014-5793(97)01546-9
Subject(s) - recombinant dna , calcium , chemistry , binding site , dissociation constant , factor ix , biophysics , biochemistry , stereochemistry , receptor , biology , organic chemistry , gene
The first EGF‐like module of human coagulation factor IX contains a single functionally important calcium ion binding site. We have now shown the dissociation constant for this site to be approximately 160 μM in a recombinant protein fragment consisting of residues 1–85 in human fIX. This represents a ≈10‐fold increase in affinity as compared with the isolated EGF module (residues 46–85). The Gla module (here with Glu instead of Gla) thus increases the affinity of the EGF module calcium ion binding site. Each of two mutations, V46E and Q50E, made to investigate whether the extra negative charge would increase the affinity of the calcium binding site manifested a negligible increase in affinity.