Braciak T A, Northemann W, Hudson G O, Shiels B R, Gehring M R, Fey G H
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, California 92037.
J Biol Chem. 1988 Mar 15;263(8):3999-4012.
cDNA clones coding for the plasma proteinase inhibitor alpha 1-inhibitor III were isolated from an acute phase rat liver library. The isolates could be divided into four groups with characteristic BamHI restriction fragment patterns. The identity of the prototype clone pRLA1I3/2J was established by comparison with the published amino acid sequence of the purified protein. It codes for a 1477-amino acid precursor polypeptide with a 24-residue signal peptide. The mature protein shares 58% overall sequence identity with rat alpha 2-macroglobulin and contains a typical internal thiolester sequence. Twenty-two of its twenty-three cysteinyl residues are conserved with alpha 2-macroglobulin implying similar tertiary structure. However, the prototype alpha 1-inhibitor III sequence differed significantly from the rat and human alpha 2-macroglobulin sequences in its bait region suggesting alpha 1-inhibitor III possesses proteinase inhibitory specificities different from those of alpha 2-macroglobulin. The variant alpha 1-inhibitor III clone pRLA1I3/2J from a second cDNA group also differed from the prototype in the bait region coding sequence, although both specify similar signal peptides and NH2 termini. The observation of variant cDNA classes suggests that acute phase rat livers produce a heterogeneous mixture of alpha 1-inhibitor III mRNA molecules. Evidence was obtained for the presence of at least four different alpha 1-inhibitor III-related genes in the rat genome. During the first 24 h of an acute phase response the abundance of hepatic alpha 1-inhibitor III mRNA was decreased 3-4-fold. This decrease was of the same order of magnitude as the reported reduction of the corresponding plasma protein concentration, suggesting that in the early phase of the acute inflammatory response the plasma concentration of this protein is mainly controlled through the abundance of its hepatic mRNA.
从急性期大鼠肝脏文库中分离出编码血浆蛋白酶抑制剂α1-抑制剂III的cDNA克隆。分离出的克隆可分为四组，具有特征性的BamHI限制性片段模式。通过与已发表的纯化蛋白氨基酸序列进行比较，确定了原型克隆pRLA1I3/2J的身份。它编码一个含有24个氨基酸信号肽的1477个氨基酸的前体多肽。成熟蛋白与大鼠α2-巨球蛋白的总体序列同一性为58%，并含有一个典型的内部硫酯序列。其23个半胱氨酸残基中有22个与α2-巨球蛋白保守，这意味着它们具有相似的三级结构。然而，原型α1-抑制剂III序列在其诱饵区域与大鼠和人类α2-巨球蛋白序列有显著差异，这表明α1-抑制剂III具有与α2-巨球蛋白不同的蛋白酶抑制特异性。来自第二个cDNA组的变异型α1-抑制剂III克隆pRLA1I3/2J在诱饵区域编码序列上也与原型不同，尽管两者都指定了相似的信号肽和NH2末端。变异cDNA类别的观察表明，急性期大鼠肝脏产生α1-抑制剂III mRNA分子的异质混合物。有证据表明大鼠基因组中存在至少四个不同的αl-抑制剂III相关基因。在急性期反应的最初24小时内，肝脏α1-抑制剂III mRNA的丰度下降了3至4倍。这种下降与报道的相应血浆蛋白浓度的降低幅度相同，这表明在急性炎症反应的早期阶段，这种蛋白的血浆浓度主要通过其肝脏mRNA的丰度来控制。
