epidermal-growth-factor and 3-hydroxyaspartic-acid

Topics: Amino Acid Sequence; Animals; Asparagine; Aspartic Acid; Blood Coagulation Factors; Calcium; Epidermal Growth Factor; Humans; Molecular Sequence Data; Structure-Activity Relationship; Vitamin K

We have recently discovered unusual sugar chains [xylose-glucose and (xylose)2-glucose] linked to a serine residue in the first epidermal growth factor (EGF)-like domains of human and bovine coagulation factors VII, IX, and protein Z. The sequence surrounding this serine residue has a common -Cys-X-Ser-X-Pro-Cys- structure. Since one (residues 533-538) of the three EGF-like domains found in human thrombospondin contains the conserved sequence, we examined the presence of such O-linked sugar chains in bovine thrombospondin (bTSP) and its 210-kDa fragment. Component sugar analysis after pyridylamination (PA) of the acid hydrolysates of the S-aminoethylated proteins revealed that the proteins contain glucose (Glc) and xylose (Xyl). The oligosaccharide moieties released from intact bTSP by hydrazinolysis followed by pyridylamination were separated into two PA-oligosaccharides by high performance liquid chromatography (HPLC). Component sugar analysis of these PA-oligosaccharides indicated that they consist of Glc and Xyl in molar ratios of 1:1 and 1:2 (or 1:3). The reducing ends of both PA-sugar chains were found to be PA-Glc, as judged from the retention time of the HPLC peak of their hydrolysates. The presence of these PA-sugar chains in bTSP was confirmed by HPLC mapping with two different columns, using standard PA-di- or PA-trisaccharide derived from coagulation factors. From these results, we concluded that bTSP contains O-linked sugar chains consisting of Glc and Xyl in one of its three EGF-like domains.

Topics: Amino Acid Sequence; Animals; Aspartic Acid; Carbohydrate Metabolism; Carbohydrate Sequence; Carbohydrates; Cattle; Chickens; Epidermal Growth Factor; Glucose; Humans; Molecular Sequence Data; Molecular Weight; Oligosaccharides; Oxidation-Reduction; Peptide Fragments; Platelet Membrane Glycoproteins; Thrombospondins; Xylose

Coagulation factor X is a vitamin K-dependent protein composed of discrete domains or modules. A proteolytically modified derivative of factor X that lacks the NH2-terminal gamma-carboxyglutamic acid (Gla)-containing region retains one Ca2+ binding site. To localize this Gla-independent Ca2+ binding site and to facilitate future studies aimed at elucidating structure-function relationship in the factor X molecule, we have devised a method to isolate the first beta-hydroxyaspartic acid (Hya)-containing epidermal growth factor (EGF)-like domain from proteolytic digests of bovine factor X performed under strictly controlled conditions. The EGF-like domain, corresponding to residues 45-86 in bovine factor X, was obtained in more than 50% recovery, and was at least 98% homogeneous as judged by NH2-terminal sequence analysis. Ca2+ binding to the isolated EGF-like domain was studied by 1H NMR spectroscopy. On binding of Ca2+ to the domain the resonances from Tyr-68 centered at 6.8 ppm were affected. The Ca2+ concentration dependence of the chemical shift was used to calculate the Ca2+ binding constant, resulting in a K alpha of 4 X 10(3) M-1 at pH 8.5 and 1 X 10(3) M-1 at pH 7.4, the higher value presumably reflecting an increase in negative surface charge due to deprotonation of a histidine residue with a pK alpha of 7.4. The NMR spectra gave no evidence of a conformational change in the EGF-like domain between pH 6 and 8.5.

Topics: Amino Acid Sequence; Animals; Aspartic Acid; Calcium; Cattle; Chromatography, Ion Exchange; Electrophoresis, Polyacrylamide Gel; Epidermal Growth Factor; Factor X; Kinetics; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Molecular Weight; Peptide Fragments; Protein Binding; Protein Conformation; Trypsin

Protein C is a vitamin K-dependent regulator of blood coagulation. It has beta-hydroxyaspartic acid in position 71 which is in the first of its two domains that are homologous to epidermal growth factor (EGF). This region has recently been demonstrated to have a Ca2+ binding site with a Kd of approximately 100 microM. Recombinant human protein C, expressed in mammalian tissue culture, had full biological activity and contained beta-hydroxyaspartic acid. Furthermore, it had a Ca2+-dependent epitope in the EGF-like domain, recognized by a monoclonal antibody. In contrast, a mutant recombinant human protein C in which beta-hydroxyaspartic acid had been replaced with glutamic acid in position 71 did not have the Ca2+-dependent epitope, and its biological activity was reduced to about 10% of normal. Fab' fragments of this antibody inhibited the anticoagulant activity of plasma-derived activated protein C, apparently by interfering with the interaction between activated protein C and its cofactor, protein S. The latter contains four tandemly arranged EGF homology domains. We propose that beta-hydroxyaspartic acid is directly involved in Ca2+ binding in protein C and in related proteins and that protein C interacts with protein S by means of its EGF homology regions.

Topics: Antibodies, Monoclonal; Aspartic Acid; Base Sequence; Calcium; Epidermal Growth Factor; Epitopes; Humans; Kinetics; Molecular Sequence Data; Protein C

All of the vitamin K-dependent plasma proteins with domains that are homologous to the epidermal growth factor (EGF) precursor have 1 hydroxylated aspartic acid residue in the NH2-terminal EGF-homology region. In addition, protein S has 1 hydroxylated asparagine residue in each of the three COOH-terminal EGF-homology regions. All of these proteins have been found to have the amino acid sequence, CX(D or N)XXXX(F or Y)XCXC (corresponding to residues 20 to 33 in EGF), where the Asp or Asn residue is hydroxylated. This sequence also appears in two of the three EGF-homology regions of the human low density lipoprotein receptor and in two of the six EGF-homology regions of bovine thrombomodulin so far identified, suggesting that they may have the modified amino acid. We have now identified beta-hydroxyaspartic acid in acid hydrolysates of both these proteins.

Topics: Adrenal Glands; Amino Acid Sequence; Animals; Asparagine; Aspartic Acid; Cattle; Epidermal Growth Factor; Molecular Sequence Data; Receptors, Cell Surface; Receptors, LDL; Receptors, Thrombin; Sequence Homology, Nucleic Acid

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.

Topics: Amino Acid Sequence; Animals; Aspartic Acid; Carboxylic Acids; Codon; Dogs; Epidermal Growth Factor; Factor IX; Factor IXa; Humans; Macromolecular Substances; Molecular Sequence Data; Mutation; Protein Processing, Post-Translational; Serine Endopeptidases

Vitamin K-dependent bovine protein S has been shown to contain a posttranslationally hydroxylated asparagine within a conserved sequence in three of its epidermal growth factor (EGF)-like domains. In a review of amino acid sequences deduced from cDNA data, we have observed that a conserved sequence containing a potential asparagine hydroxylation site exists within EGF-like domains of a variety of functionally diverse proteins. We have studied a number of these and report the presence of erythro-beta-hydroxyasparagine (e-beta Hyn) in three non-vitamin K-dependent proteins: the plasma complement proteins C1r and C1s (where overbar indicates activated form) and the urinary protein uromodulin. For each protein, e-beta Hyn was identified in enzyme digests following the initial observation of erythro-beta-hydroxyaspartic acid (e-beta Hya) in acid hydrolysates of the proteins. e beta Hya and e-beta Hyn residues are detected by a postcolumn derivatization cation-exchange HPLC method herein described. HPLC isolation of the presumptive e-beta Hyn residue from enzyme digests of intact C1r allowed confirmation of its structure by GC/MS. Based upon available cDNA sequence data and observation of e-beta Hya in acid hydrolysates, we suggest other proteins in which e-beta Hyn may occur.

Topics: Asparagine; Aspartic Acid; Chromatography, High Pressure Liquid; Complement Activating Enzymes; Complement C1; Complement C1r; Complement C1s; Epidermal Growth Factor; Gas Chromatography-Mass Spectrometry; Humans; Mucoproteins; Protein Processing, Post-Translational; Sequence Homology, Nucleic Acid; Uromodulin