The role of beta‐hydroxyaspartate and adjacent carboxylate residues in the first EGF domain of human factor IX

beta‐Hydroxyaspartic acid is a post‐translationally modified amino acid found in a number of plasma proteins in a domain homologous to epidermal growth factor. Its presence can be correlated with a high affinity Ca2+ binding site, with a dissociation constant of 10‐100 microM. We describe a system f...

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Bibliographic Details
Published in:The EMBO journal 1988-07, Vol.7 (7), p.2053-2061
Main Authors: Rees, D. J., Jones, I. M., Handford, P. A., Walter, S. J., Esnouf, M. P., Smith, K. J., Brownlee, G. G.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Aspartic Acid - analogs & derivatives
Aspartic Acid - metabolism
Biological and medical sciences
Blood coagulation. Blood cells
Carboxylic Acids - metabolism
coagulation factor IX
Coagulation factors
Codon
Dogs
Epidermal Growth Factor - genetics
Factor IX - genetics
Factor IX - isolation & purification
Factor IX - metabolism
Factor IXa
Fundamental and applied biological sciences. Psychology
Humans
Macromolecular Substances
man
Molecular and cellular biology
Molecular Sequence Data
Mutation
Protein Processing, Post-Translational
Serine Endopeptidases - metabolism
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Summary:beta‐Hydroxyaspartic acid is a post‐translationally modified amino acid found in a number of plasma proteins in a domain homologous to epidermal growth factor. Its presence can be correlated with a high affinity Ca2+ binding site, with a dissociation constant of 10‐100 microM. We describe a system for the expression of human coagulation factor IX in dog kidney cells in tissue culture, in which the post‐translational modifications and the biochemical activity are indistinguishable from factor IX synthesized in vivo. This system has been used to express eight different point mutations of human factor IX in the first epidermal growth factor domain in order to study the role of beta‐hydroxyaspartate at residue 64, and the adjacent carboxylate residues at positions 47, 49 and 78. We conclude that this domain is essential for factor IX function and suggest that Ca2+ binds to carboxylate ions in this domain and stabilizes a conformation necessary for the interaction of factor IXa with factor X, factor VIII and phospholipid in the next step of the clotting cascade.
ISSN:0261-4189
1460-2075
DOI:10.1002/j.1460-2075.1988.tb03045.x