The related tyrosine phosphatase-like proteins (PTP) IA-2 and IA-2beta are autoantigens of type 1 diabetes. Autoantibodies are predominantly against IA-2. We utilized the close homology between IA-2 and IA-2beta PTP domains to design chimeras and mutants in order to identify humoral IA-2-specific epitopes. Fifteen sera with antibodies to IA-2 specific PTP domain epitopes were tested against IA-2beta(741-848)/IA-2(795-889)/IA-2beta(943-1033), IA-2beta(741-848)/IA-2(795-845)/IA-2beta(900-1033), and IA-2beta(741-898)/IA-2(845-875)/IA-2beta(930-1033)chimeras. Two sera bound IA-2beta(741-848)/IA-2(795-889)/IA-2beta(943-1033)and IA-2beta(741-848)/IA-2(795-845)/IA-2beta(900-1033)only indicating that the IA-2 specific residues 859, 862, and/or 867 were critical for antibody binding. Mutation of glutamine 862 abolished binding in one of these sera. Seven sera bound only the IA-2beta(741-848)/IA-2(795-889)/IA-2beta(943-1033)chimera, indicating that binding required IA-2 specific amino acids within both 795-845 and 846-875, or that IA-2 residues 876-888 were important for binding. Mutation of glutamine 862 abolished binding in two of these sera, and mutation of residues 876, 877, 878, and 880 markedly reduced binding in two others. Six sera bound all three chimeras indicating that they contained multiple IA-2 specific PTP domain antibodies. In three of these sera, mutation of residues at positions 876, 877, 878, 880, and/or residues 862 and 822 reduced antibody binding by more than 50%. These findings indicate that glutamine at position 862, and residues 876-880 of the WPD loop of IA-2 are important for several of the IA-2 specific PTP domain epitopes.

中文翻译：

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糖尿病相关的IA-2特异性自身抗体的精细定位。

相关的酪氨酸磷酸酶样蛋白（PTP）IA-2和IA-2beta是1型糖尿病的自身抗原。自身抗体主要针对IA-2。我们利用IA-2和IA-2beta PTP域之间的紧密同源性来设计嵌合体和突变体，以鉴定体液IA-2特异性表位。针对IA-2beta（741-848）/ IA-2（795-889）/ IA-2beta（943-1033），IA-2beta（741-848）测试了具有IA-2特异性PTP域表位抗体的15个血清/ IA-2（795-845）/ IA-2beta（900-1033）和IA-2beta（741-898）/ IA-2（845-875）/ IA-2beta（930-1033）嵌合体。两个血清结合的IA-2beta（741-848）/ IA-2（795-889）/ IA-2beta（943-1033）和IA-2beta（741-848）/ IA-2（795-845）/ IA- 2beta（900-1033）仅表明IA-2特定残基859、862和/或867对于抗体结合至关重要。谷氨酰胺862的突变消除了这些血清之一中的结合。七个血清仅结合IA-2beta（741-848）/ IA-2（795-889）/ IA-2beta（943-1033）嵌合体，表明结合需要795-845和846中的IA-2特定氨基酸-875，或IA-2残基876-888对于结合很重要。谷氨酰胺862的突变消除了这些血清中两个的结合，而残基876、877、878和880的突变显着降低了另外两个血清的结合。六个血清结合了所有三个嵌合体，表明它们含有多种IA-2特异性PTP域抗体。在这些血清中的三个中，876、877、878、880位残基和/或862和822位残基的突变使抗体结合降低了50％以上。这些发现表明，IA-2的WPD环的862位和876-880位残基对于一些IA-2特异性PTP结构域表位很重要。