Complete amino acid sequence of the light chain of human blood coagulation factor X: evidence for identification of residue 63 as .beta.-hydroxyaspartic acid

Abstract

The complete amino acid sequence of the light chain of human blood coagulation factor X has been determined by automated Edman degradation of peptides isolated from chemical and enzymatic digests of the carboxymethylated light chain. The protein consists of 139 amino acid residues, which include 11 residues of gamma-carboxyglutamic acid. The first 100 residues of the human factor X light chain exhibit approximately 80% homology when compared to the amino-terminal sequence of bovine factor X light chain. This homology decreases to approximately 50% in the remaining 39 residues of the carboxyl-terminal region of the protein. Proton nuclear magnetic resonance spectroscopy and mass spectrometry analyses of isolated residue 63 identified this residue as L-erythro-beta-hydroxyaspartic acid, a hitherto unrecognized amino acid in proteins. Evidence is also presented for the presence of this residue in the corresponding regions of the light chains of bovine factor X and bovine protein C. The biological function of beta-hydroxyaspartic acid in these proteins is unknown.

Identification of erythro‐β‐hydroxyasparagine in the EGF‐like domain of human C1r

“…This vitamin K-dependent protein contains 3 ,&hydroxyasparagine residues which, like residues 150 of human Clr [4], are all located in sequences homologous to the EGF precursor. Several cases of &hydroxyaspartic acid residues have also been described in a number of other vitamin K-dependent proteins, including protein C [18,19], factors VII, IX and X [20,23] and again, these residues all occur in EGF-like sequences. A consensus sequence representing the structural requirements of the enzyme(s) responsible for the hydroxylation of these aspartic acid or asparagine residues has recently been proposed by Stenflo et al (171.…”

Factor XSanto Domingo. Evidence that the severe clinical phenotype arises from a mutation blocking secretion.

“…Thus, the defect in the signal sequence of Daub D exerts its effect posttranscriptionally. F7so Do_ is the first described example of a bleeding diathesis due to a mutation in the (2)(3)(4)(5). The gene has also been isolated and partially characterized.…”

Defining the Factor Xa-binding Site on Factor Va by Site-directed Glycosylation

“…FVIIIa is a cofactor to FIXa in the activation of FX, a reaction that in many respects is very similar to the prothrombin activation (2). After activation of FX, the light chain (18 kDa) containing the Gla and two epidermal growth factor-like domains remains associated via a disulfide bridge to the heavy chain (27 kDa) composed of the serine-protease domain (15,16).…”