Tyrosine 69 of the first epidermal growth factor-like domain of human factor IX is essential for clotting activity.
Epidermal growth factor (EGF)-like domains are present in many extracellular proteins including clotting factor IX. Those EGF-like domains with the consensus amino acid residues Asp/Asn, Asp/Asn, Asp*/Asn*, Tyr/Phe (where * denotes a beta-hydroxylated residue) bind calcium. Previous NMR studies of the isolated first EGF-like domain of human factor IX suggested that the first 3 consensus residues Asp-47, Asp-49, and Asp-64 were direct ligands for calcium. We now show from mutagenesis studies that Tyr-69 is not a direct ligand for calcium but is essential for the clotting activity of intact factor IX, specifically for the factor VIIIa-dependent activation of factor X. Surprisingly, Tyr-69 is not required for beta-hydroxylation of Asp-64.
Hughes
P E
PE
Sir William Dunn School of Pathology, University of Oxford, United Kingdom.
Morgan
G
G
Rooney
E K
EK
Brownlee
G G
GG
Handford
P
P
D000595:Amino Acid Sequence; D001483:Base Sequence; D001777:Blood Coagulation; D002118:Calcium / Q000494:pharmacology; D002846:Chromatography, Affinity; D004220:Disulfides / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000737:chemistry*; D005164:Factor IX / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D015949:Factor IXa / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008961:Models, Structural; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014443:Tyrosine
D004220:Disulfides; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D014443:Tyrosine; D004815:Epidermal Growth Factor; D005164:Factor IX; D005170:Factor X; D015949:Factor IXa; D002118:Calcium