The role of beta‐hydroxyaspartate and adjacent carboxylate residues in the first EGF domain of human factor IX.
The role of beta‐hydroxyaspartate and adjacent carboxylate residues in the first EGF domain of human factor IX.
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DOI：
10.1002/j.1460-2075.1988.tb03045.x
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发表时间：
1988-07
期刊：
影响因子：
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通讯作者：
D. J. G. Rees;Ian M. Jones;P. Handford;S. J. Walter;M. P. Esnouf;K. J. Smith;George G. Brownlee
中科院分区：
文献类型：
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作者：
D. J. G. Rees;Ian M. Jones;P. Handford;S. J. Walter;M. P. Esnouf;K. J. Smith;George G. Brownlee
β-羟基天冬氨酸是一种在许多血浆蛋白中发现的与表皮生长因子同源的结构域中的后修饰氨基酸。它的存在可能与高亲和力的Ca 2+结合位点相关，解离常数为10 - 100 μ M。我们描述了一种在组织培养的狗肾细胞中表达人凝血因子IX的系统，其中翻译后修饰和生化活性与体内合成的因子IX无法区分。该系统已用于表达人因子IX在第一表皮生长因子结构域中的8个不同点突变，以研究残基64处的β-羟基天冬氨酸以及位置47、49和78处的相邻羧酸残基的作用。我们的结论是，这个域是必不可少的因子IX的功能，并建议，Ca 2+结合羧酸根离子在这个域和稳定的构象必要的因子IXa与因子X，因子VIII和磷脂的相互作用在凝血级联的下一步。
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.