Jensen P H, Schüler E, Woodrow G, Richardson M, Goss N, Højrup P, Petersen T E, Rasmussen L K
Department of Medical Biochemistry, University of Aarhus, Denmark.
J Biol Chem. 1994 May 27;269(21):15394-8.
Plasminogen activator inhibitor type 2 (PAI-2) prevents fibrinolysis by blocking plasminogen activators. It is expressed principally by trophoblast cells and macrophages. PAI-2 in trophoblast membranes has been found cross-linked to large complexes apparently catalyzed by trophoblast transglutaminase (Jensen, P. H., Lorand, L., Ebbesen, P., and Gliemann, J. (1993) Eur. J. Biochem. 214, 141-146). Recombinant human PAI-2 was labeled with [14C]putrescine catalyzed by guinea pig liver transglutaminase. The [14C]putrescine-labeled PAI-2 was digested with cyanogen bromide and trypsin, and the peptides were purified by reverse-phase high performance chromatography. Amino acid sequencing and plasma desorption mass spectrometry of the labeled peptides revealed [14C]putrescine incorporation at Gln83, Gln84, and Gln86. These residues are present in a PAI-2-specific region of 33 amino acids that is inserted between helices C and D and which probably represents a unique solvent-exposed domain. A PAI-2 mutant lacking this insertion was determined not to be a substrate for transglutaminase by [14C]putrescine incorporation and could not form transglutaminase-catalyzed polymers. Thus, the unique PAI-2 insertion represents a functional domain that, by virtue of its transglutaminase acceptor sites, allows participation in binding reactions without affecting the inhibitory function of PAI-2.
2型纤溶酶原激活物抑制剂（PAI-2）通过阻断纤溶酶原激活物来防止纤维蛋白溶解。它主要由滋养层细胞和巨噬细胞表达。已发现滋养层细胞膜中的PAI-2与明显由滋养层转谷氨酰胺酶催化形成的大复合物交联（詹森，P.H.，洛兰德，L.，埃贝森，P.，和格利曼，J.（1993年）《欧洲生物化学杂志》214卷，第141 - 146页）。重组人PAI-2用豚鼠肝脏转谷氨酰胺酶催化的[14C]腐胺进行标记。用溴化氰和胰蛋白酶消化[14C]腐胺标记的PAI-2，肽段通过反相高效液相色谱法纯化。对标记肽段进行氨基酸测序和等离子体解吸质谱分析，结果显示[14C]腐胺掺入到第83位、第84位和第86位谷氨酰胺处。这些残基存在于一个33个氨基酸的PAI-2特异性区域中，该区域插入在螺旋C和螺旋D之间，可能代表一个独特的溶剂暴露结构域。通过[14C]腐胺掺入确定，缺少该插入序列的PAI-2突变体不是转谷氨酰胺酶的底物，并且不能形成转谷氨酰胺酶催化的聚合物。因此，独特的PAI-2插入序列代表一个功能结构域，凭借其转谷氨酰胺酶受体位点，它能够参与结合反应而不影响PAI-2的抑制功能。
