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The low p K a value of iron‐binding ligand Tyr188 and its implication in iron release and anion binding of human transferrin
Author(s) -
Sun Xuesong,
Sun Hongzhe,
Ge Ruiguang,
Richter Megan,
Woodworth Robert C.,
Mason Anne B.,
He Qing-Yu
Publication year - 2004
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/j.febslet.2004.07.076
Subject(s) - transferrin , chemistry , titration , binding site , tyrosine , plasma protein binding , ligand (biochemistry) , chelation , arsenate , biochemistry , stereochemistry , crystallography , arsenic , inorganic chemistry , receptor , organic chemistry
2D NMR–pH titrations were used to determine p K a values for four conserved tyrosine residues, Tyr45, Tyr85, Tyr96 and Tyr188, in human transferrin. The low p K a of Tyr188 is due to the fact that the iron‐binding ligand interacts with Lys206 in open‐form and with Lys296 in the closed‐form of the protein. Our current results also confirm the anion binding of sulfate and arsenate to transferrin and further suggest that Tyr188 is the actual binding site for the anions in solution. These data indicate that Tyr188 is a critical residue not only for iron binding but also for chelator binding and iron release in transferrin.