Chen Meng-Yi, Hu Kuang-Yu, Huang Chih-Cheng, Song Yen-Ling
Institute of Zoology, National Taiwan University, Taipei 106, Taiwan.
Dev Comp Immunol. 2005;29(12):1003-16. doi: 10.1016/j.dci.2005.03.012.
Coagulation (clot formation) forms a physical barrier to prevent the loss of body fluid and dissemination of microbes into the haemocoel after injury or infection. Its quickness and efficiency are essential for the survival of invertebrates that rely solely on innate immunity. Transglutaminase (TG) catalyses intermolecular or intramolecular epsilon-(gamma-glutamyl) lysine bond formation, resulting in a protein polymerisation, and plays a role in blood coagulation and post-translational protein remodelling. In the present study, we cloned a TG from shrimp (Penaeus monodon) haemocyte cDNA. It was assigned as shrimp transglutaminase II (STG II). The STG II cDNA consists of a coding region of 2,274bp. The deduced protein has 757 amino acid residues with a calculated molecular mass of 85,000 Da and an isoelectric point of 5.48. RT-PCR results showed a significant level of STG II expression in haemocytes but not in hepatopancreas, in contrast to shrimp STG I (AY074924.1). The genetic distance between STG II and STG I is much larger than the distance between STG II and the TG of the kuruma shrimp (Marsupenaeus japonicus). Evidence based on tissue distribution and genetic distance suggests that no less than two types of shrimp TG exist that are encoded at different chromosomal locations. The recombinant STG II (rSTG II) incorporated a TG-specific substrate, dansylcadaverine (DCA), into clottable proteins (CP) in a calcium dependent manner. Other haemocyte- or plasma-derived TG substrate is not required for CP polymerisation but may be necessary for stable clot formation. The rSTG II catalysed clottable proteins into a long chain under transmission electron microscopy (TEM) observation. In conclusion, STG II is characterized as a haemocyte TG and is involved in coagulation.
凝血（凝块形成）形成一道物理屏障，以防止受伤或感染后体液流失以及微生物扩散至血腔。其速度和效率对于仅依赖先天免疫的无脊椎动物的生存至关重要。转谷氨酰胺酶（TG）催化分子间或分子内ε-（γ-谷氨酰基）赖氨酸键的形成，导致蛋白质聚合，并在血液凝固和翻译后蛋白质重塑中发挥作用。在本研究中，我们从虾（斑节对虾）血细胞cDNA中克隆了一种TG。它被命名为虾转谷氨酰胺酶II（STG II）。STG II cDNA由一个2274bp的编码区组成。推导的蛋白质有757个氨基酸残基，计算分子量为85,000 Da，等电点为5.48。逆转录聚合酶链反应（RT-PCR）结果显示与虾STG I（AY074924.1）相反，STG II在血细胞中有显著表达水平，但在肝胰腺中无表达。STG II与STG I之间的遗传距离远大于STG II与日本对虾（凡纳滨对虾）的TG之间的距离。基于组织分布和遗传距离的证据表明，至少存在两种在不同染色体位置编码且类型不同的虾TG。重组STG II（rSTG II）以钙依赖的方式将TG特异性底物丹磺酰尸胺（DCA）掺入可凝蛋白（CP）中。CP聚合不需要其他血细胞或血浆来源的TG底物，但可能对稳定凝块形成是必需的。在透射电子显微镜（TEM）观察下，rSTG II将可凝蛋白催化成一条长链。总之，STG II被鉴定为一种血细胞TG，并参与凝血过程。
