Fujikawa K, Chung D W, Hendrickson L E, Davie E W
Biochemistry. 1986 May 6;25(9):2417-24. doi: 10.1021/bi00357a018.
A lambda gtll cDNA library prepared from human liver poly(A) RNA has been screened with affinity-purified antibody to human factor XI, a blood coagulation factor composed of two identical polypeptide chains linked by a disulfide bond(s). A cDNA insert coding for factor XI was isolated and shown to contain 2097 nucleotides, including 54 nucleotides coding for a leader peptide of 18 amino acids and 1821 nucleotides coding for 607 amino acids that are present in each of the 2 chains of the mature protein. The cDNA for factor XI also contained a stop codon (TGA), a potential polyadenylation or processing sequence (AACAAA), and a poly(A) tail at the 3' end. Five potential N-glycosylation sites were found in each of the two chains of factor XI. The cleavage site for the activation of factor XI by factor XIIa was identified as an internal peptide bond between Arg-369 and Ile-370 in each polypeptide chain. This was based upon the amino acid sequence predicted by the cDNA and the amino acid sequence previously reported for the amino-terminal portion of the light chain of factor XI. Each heavy chain of factor XIa (369 amino acids) was found to contain 4 tandem repeats of 90 (or 91) amino acids plus a short connecting peptide. Each repeat probably forms a separate domain containing three internal disulfide bonds. The light chains of factor XIa (each 238 amino acids) contain the catalytic portion of the enzyme with sequences that are typical of the trypsin family of serine proteases. The amino acid sequence of factor XI shows 58% identity with human plasma prekallikrein.
用人肝聚腺苷酸RNA构建的λgtll cDNA文库，已用针对人因子XI的亲和纯化抗体进行筛选。因子XI是一种血液凝固因子，由两条通过二硫键相连的相同多肽链组成。分离出编码因子XI的cDNA插入片段，其长度为2097个核苷酸，包括编码18个氨基酸的前导肽的54个核苷酸，以及编码成熟蛋白两条链中每条链上607个氨基酸的1821个核苷酸。因子XI的cDNA在3'端还含有一个终止密码子（TGA）、一个潜在的聚腺苷酸化或加工序列（AACAAA）以及一个聚腺苷酸尾巴。在因子XI的两条链中均发现了五个潜在的N-糖基化位点。因子XIIa激活因子XI的切割位点被确定为每条多肽链中Arg-369和Ile-370之间的一个内部肽键。这是基于cDNA预测的氨基酸序列以及先前报道的因子XI轻链氨基末端部分的氨基酸序列。发现因子XIa的每条重链（369个氨基酸）含有4个90（或91）个氨基酸的串联重复序列以及一个短连接肽。每个重复序列可能形成一个包含三个内部二硫键的单独结构域。因子XIa的轻链（每条238个氨基酸）包含该酶的催化部分，其序列是丝氨酸蛋白酶胰蛋白酶家族的典型序列。因子XI的氨基酸序列与人血浆前激肽释放酶具有58%的同一性。
