Guinto E R, Esmon C T, Mann K G, MacGillivray R T
Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City 73104.
J Biol Chem. 1992 Feb 15;267(5):2971-8.
Lack of availability of a primary structure for bovine factor V has hindered detailed analysis of a vast majority of structure-function correlations on this molecule. To determine the primary structure of bovine factor V, we used liver mRNA as a template for the synthesis of three cDNA libraries. The sequences of seven overlapping cDNA clones infer two bovine factor V variants. Variant 1 results in a 6910-basepair (bp) cDNA including 103 bp of 5'-untranslated sequence, 6633 bp of coding sequence and 171 bp of 3'-untranslated sequence with a putative polyadenylation site. Variant 2 differs only in the size of the coding sequence (6618 bp). The open reading frame translates to factor V consisting of 2211 (or 2206) amino acids including a 28-amino acid signal peptide. Comparison of the amino acid sequences with human factor Va reveals 84% identity for the heavy and 86% for the light chains. In contrast, the B domain (connecting region) exhibits only 59% identity relative to the human molecule. The bovine B domain contains two repeats of a 14-amino acid structure that is contained only once in the human sequence. Bovine factor V lacks one of the nine amino acid repeats and one of the 17 amino acid repeats present in the human B domain. Factor V has little homology to the factor VIII molecule in the B domain. The 17-amino acid repeat missing in bovine factor V allows identification of an 18-amino acid sequence that is homologous to the B domain of human factor VIII. These 18 amino acids may either constitute the unique vestige of a divergent evolution between the B domains of factors V and VIII or reveal the convergent evolution toward a critical epitope involved in the activation of both procofactors.
牛因子V一级结构的缺失阻碍了对该分子绝大多数结构-功能相关性的详细分析。为了确定牛因子V的一级结构，我们以肝脏mRNA为模板合成了三个cDNA文库。七个重叠cDNA克隆的序列推断出两种牛因子V变体。变体1产生一个6910碱基对（bp）的cDNA，包括103 bp的5'-非翻译序列、6633 bp的编码序列和171 bp的3'-非翻译序列以及一个假定的聚腺苷酸化位点。变体2仅在编码序列大小上有所不同（6618 bp）。开放阅读框翻译为包含2211（或2206）个氨基酸的因子V，其中包括一个28个氨基酸的信号肽。将氨基酸序列与人因子Va进行比较，重链的同源性为84%，轻链为86%。相比之下，B结构域（连接区）与人分子的同源性仅为59%。牛B结构域包含一个14个氨基酸结构的两个重复序列，而该结构在人类序列中仅出现一次。牛因子V缺少人类B结构域中存在的九个氨基酸重复序列之一和十七个氨基酸重复序列之一。因子V在B结构域与因子VIII分子几乎没有同源性。牛因子V中缺失的十七个氨基酸重复序列使得能够鉴定出一个与人类因子VIII的B结构域同源的18个氨基酸序列。这18个氨基酸可能要么构成因子V和VIII的B结构域之间趋异进化的独特遗迹，要么揭示了朝向参与两种前辅因子激活的关键表位的趋同进化。
