McGraw R A, Davis L M, Lundblad R L, Stafford D W, Roberts H R
Clin Haematol. 1985 Jun;14(2):359-83.
The genetics of haemophilia B and the structure-function relationships of factor IX interactions with cofactors and substrates have been reviewed. Emphasis has been placed on contributions to our understanding made by analysis of variants. Amino acid substitutions at or near the site of activation lead to inactive factor IX or to factor IX species with decreased clotting activity. Release of the activation peptide is necessary for optimal interaction of factor IX with its cofactors and substrates. Abnormalities in the calcium binding region, whether Gla independent or dependent, also decrease clotting activity. The defects in haemophilia Bm variants somehow affect factor VII-tissue factor interactions with factor X. Other mutations may affect the factor IX heavy chain, probably at or near the active site. Amino acid substitutions may cause conformational changes in factor IX that interfere with other interactions such as with antithrombin III and factor VIII. Recombinant DNA techniques have been employed to analyse normal and abnormal factor IX genes. DNA sequence analysis of factor IX cDNA clones revealed the primary structure of the mature protein and a predicted leader peptide. Knowledge of the primary sequence of factor IX allowed identification of the specific defect in the factor IX Chapel Hill variant. Analysis of normal factor IX genomic clones has determined that the 35 kb gene is composed of eight coding exons and seven intervening sequences. Sequence analysis of the CRM+ variants will identify mutations disrupting the normal interactions of factor IX. Southern analysis of CRM- variants has revealed gross factor IX gene deletions in some cases. Such deletions have been employed for carrier deletion in some families. Restriction fragment length polymorphisms in the factor IX gene have also proven useful for carrier identification. Manipulations of the cloned factor IX gene to make specific mutations in vitro and improvements in the technology for expression of deliberately modified genes will further elucidate the relationships between factor IX structure and function.
血友病B的遗传学以及凝血因子IX与辅因子和底物相互作用的结构-功能关系已得到综述。重点在于分析变异体对我们理解所做的贡献。激活位点处或其附近的氨基酸替换会导致凝血因子IX无活性或凝血活性降低的凝血因子IX种类。激活肽的释放对于凝血因子IX与其辅因子和底物的最佳相互作用是必要的。钙结合区域的异常，无论是否依赖γ-羧基谷氨酸（Gla），也会降低凝血活性。Bm型血友病变异体中的缺陷以某种方式影响因子VII-组织因子与因子X的相互作用。其他突变可能影响凝血因子IX重链，可能在活性位点处或其附近。氨基酸替换可能导致凝血因子IX构象变化，从而干扰其他相互作用，如与抗凝血酶III和因子VIII的相互作用。已采用重组DNA技术分析正常和异常的凝血因子IX基因。凝血因子IX cDNA克隆的DNA序列分析揭示了成熟蛋白的一级结构和预测的前导肽。凝血因子IX一级序列的知识使得能够鉴定出凝血因子IX教堂山变异体中的特定缺陷。对正常凝血因子IX基因组克隆的分析已确定35 kb的基因由8个编码外显子和7个间隔序列组成。CRM+变异体的序列分析将鉴定破坏凝血因子IX正常相互作用的突变。CRM-变异体的Southern分析在某些情况下揭示了凝血因子IX基因的大片段缺失。这种缺失已在一些家族中用于携带者缺失检测。凝血因子IX基因中的限制性片段长度多态性也已被证明对携带者鉴定有用。对克隆的凝血因子IX基因进行体外特定突变的操作以及改进故意修饰基因的表达技术将进一步阐明凝血因子IX结构与功能之间的关系。
