Oiso M, Nishi T, Ishikawa T, Nishimura Y, Matsushita S
Department of Neuroscience and Immunology, Kumamoto University Graduate School of Medical Sciences, Japan.
Hum Immunol. 1997 Jan;52(1):47-53. doi: 10.1016/s0198-8859(96)00253-4.
HLA-DQ8 (DQA10302-DQB10302: DQ beta 57 Ala) and (DQA10302-DQB10303: DQ beta 57 Asp) differ only at beta 57, at which polymorphism reportedly confers distinct susceptibility to insulin-dependent diabetes mellitus (IDDM). To identify the differential peptide binding affected by beta 57, we determined DQ9-binding peptides by affinity-based selection of a phage random peptide library using the biotinylated DQ9 complex. Nonconservative single-residue substitution of high-affinity DQ8- and DQ9-binding peptide (1KLPDYVLWSSSTVVGLGAAGA21) at the underlined residues significantly decreased the peptide binding to DQ8 and DQ9. Affinities of the wild-type 21-mer K4DYVLWSSSTV13 and K4AYAAWAAATA13 to DQ8 and DQ9 were practically the same. The K4DYVLWSSSTV13-based analogue peptides with substitutions at 12T showed that residues R, K, H, E, D, Q, N, T, S, V, L, I, F, M, W, and Y permitted binding to DQ8, whereas only R, T, V, L, I, F, M, W, and Y did so to DQ9. Thus, significant differences exist between DQ9 and DQ8, in that the majority of polar residues, regardless of their static charges at the residue 12, permitted binding to IDDM-susceptible DQ8, which is not the case for DQ9. The affinities of K4DYVLWSSSXV13 AND K4AYAAWAAAAX13 (where X is T, A, K, D, or I) were almost equal to DQ8 and DQ9, suggesting the DQ8- and DQ9-binding peptide motifs could accept both the 8-mer and 9-mer frames depending on intervening sequences between N- and C-terminal anchor residues. The biochemical basis of peptide-HLA interactions determined by DQ beta 57 is discussed.
HLA-DQ8（DQA10302-DQB10302：DQβ57位为丙氨酸）和（DQA10302-DQB10303：DQβ57位为天冬氨酸）仅在β57位不同，据报道该多态性赋予了对胰岛素依赖型糖尿病（IDDM）不同的易感性。为了确定受β57影响的差异肽结合情况，我们通过使用生物素化的DQ9复合物基于亲和力筛选噬菌体随机肽库来确定DQ9结合肽。对高亲和力的DQ8和DQ9结合肽（1KLPDYVLWSSSTVVGLGAAGA21）下划线处的残基进行非保守单残基替换，显著降低了该肽与DQ8和DQ9的结合。野生型21肽K4DYVLWSSSTV13和K4AYAAWAAATA13与DQ8和DQ9的亲和力实际上是相同的。以K4DYVLWSSSTV13为基础在12T处进行替换的类似肽表明，残基R、K、H、E、D、Q、N、T、S、V、L、I、F、M、W和Y允许与DQ8结合，而只有R、T、V、L、I、F、M、W和Y允许与DQ9结合。因此，DQ9和DQ8之间存在显著差异，即大多数极性残基，无论其在12位的静电荷如何，都允许与IDDM易感的DQ8结合，而DQ9则不然。K4DYVLWSSSXV13和K4AYAAWAAAAX13（其中X为T、A、K、D或I）与DQ8和DQ9的亲和力几乎相等，表明DQ8和DQ9结合肽基序可根据N端和C端锚定残基之间的间隔序列接受8肽和9肽框架。本文讨论了由DQβ57决定的肽与HLA相互作用的生化基础。
