Catalytic domain of PDC-E2 contains epitopes recognized by antimitochondrial antibodies in primary biliary cirrhosis

AIM:To search for further immunodominant peptides of the pyruvate dehydrogenase complex E2-component (PDC-E2) recognized by antimitochondrial antibodies (AMA) in primary biliary cirrhosis (PBC). METHODS:Sera from 95 patients with PBC were tested by enzyme-linked immunosorbent assay against 33 synthetic overlapping peptides (25 amino acids; aa) covering the entire length of the E2-subunit of PDC-E2. Furthermore,the inner lipoyl peptide 167-184 was used in an unlip oylated and a lipoylated form as well as coupled to ovalbumin. Sera from 11 AMA negative/ANA posit ive PBC patients,63 patients with other liver disorders and 22 healthy blood donors served as controls.RESULTS:Of the 95 PBC-sera,74% reacted with the peptide 475-499 and 58% with the pept ide 407-431 located within the catalytic domain of PDC-E2. Patients with other disorders or healthy controls were positive in only up to 18%. Antibodies to the unlipoylatedand lip oylated pept ide 167-184 within the inner lipoyl domain were found in only 5% and 11% of the PBC sera,respectively; using ovalbumin-coupled peptides,the incidence increased up to 57% (unlipoylated form). CONCLUSION:Peptides within the catalytic site of PDC-E2 rather than the previously reported lipoyl binding peptide 167-184 may represent major immunodomin ant epitopes recognized by AMA in PBC.

ITm活性转座子及其结构特征分析

ITm超家族是真核生物基因组中分布最广泛的DNA转座子家族之一,它们以DNA为媒介,通过"剪切–粘贴"机制在基因组中不断跳跃,引起基因组的重组与突变。随着对ITm转座子的深入研究,许多ITm转座子逐渐成为基因克隆、基因表达及其功能研究的重要工具。该文对活性ITm转座子作了较为全面的研究,并对其结构、拷贝数、分布以及转座特性进行了系统归纳,分析了活性ITm转座子螺旋–转角–螺旋(helix-turn-helix,HTH)结构,天冬氨酸–天冬氨酸–天冬氨酸/谷氨酸(Asp-Asp-Asp/Glu,DDD/E)催化结构域、Linker、核定位信号(nuclear localization sequence,NLS)及末端反向重复序列(terminal inverted repeats,TIRs)的序列特征。结果表明,自主转座活性的ITm转座子必须具备完整的转座酶及TIRs,上述结构及序列的突变均会不同程度的对转座子活性产生影响。这为活性ITm转座子的鉴定及功能分析奠定了重要基础,同时,也为人工调控ITm转座子转座活性提供了理论依据。