Doebele R C, Busch R, Scott H M, Pashine A, Mellins E D
School of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
Immunity. 2000 Oct;13(4):517-27. doi: 10.1016/s1074-7613(00)00051-0.
HLA-DM removes CLIP and other loosely bound peptides from MHC class II molecules. The crystal structures of class II molecules and of HLA-DM have not permitted identification of their interaction sites. Here, we describe mutations in class II that impair interactions with DM. Libraries of randomly mutagenized DR3 alpha and beta chains were screened for their ability to cause cell surface accumulation of CLIP/DR3 complexes in EBV-B cells. Seven mutations were associated with impaired peptide loading in vivo, as detected by SDS stability assays. In vitro, these mutant DR3 molecules were resistant to DM-catalyzed CLIP release and showed reduced binding to DM. All mutations localize to a single lateral face of HLA-DR, which we propose interacts with DM during peptide exchange.
HLA-DM从MHC II类分子中去除CLIP和其他松散结合的肽段。II类分子和HLA-DM的晶体结构尚未明确它们的相互作用位点。在此，我们描述了II类分子中影响与DM相互作用的突变。通过筛选随机诱变的DR3α链和β链文库，检测其在EBV-B细胞中导致CLIP/DR3复合物在细胞表面积累的能力。通过SDS稳定性分析检测到，七个突变与体内肽段装载受损有关。在体外，这些突变的DR3分子对DM催化的CLIP释放具有抗性，并且与DM的结合减少。所有突变均定位于HLA-DR的单个侧面，我们推测在肽段交换过程中该侧面与DM相互作用。
