Hedley M L, Urban R G, Strominger J L
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138.
Proc Natl Acad Sci U S A. 1994 Oct 25;91(22):10479-83. doi: 10.1073/pnas.91.22.10479.
In vitro transcription/translation of HLA-DR1 cDNAs in the presence of microsomal membranes was used to study the association of major histocompatibility complex class II molecules with peptide and invariant chain (Ii) in the endoplasmic reticulum (ER). HLA-DR alpha and HLA-DR beta subunits assembled into SDS-unstable heterodimers in the absence of exogenous peptide. The inclusion of synthetic peptides during the alpha/beta assembly process promoted their conversion to SDS-resistant heterodimers. Addition of Ii RNA during the translation of HLA-DR alpha and HLA-DR beta RNAs resulted in the formation of alpha/beta/Ii complexes. Peptide binding by class II molecules was detected even when excess Ii was present during alpha/beta assembly. These findings indicate that peptides can bind alpha/beta heterodimers in the ER microenvironment and suggest that peptides derived from cytosolic proteins that are presented by class II molecules at the cell surface may have bound to HLA-DR in the ER.
在微粒体膜存在的情况下，对HLA - DR1互补DNA（cDNA）进行体外转录/翻译，以研究主要组织相容性复合体II类分子在内质网（ER）中与肽和恒定链（Ii）的关联。在没有外源性肽的情况下，HLA - DRα和HLA - DRβ亚基组装成SDS不稳定的异二聚体。在α/β组装过程中加入合成肽促进它们转化为SDS抗性异二聚体。在HLA - DRα和HLA - DRβ RNA翻译过程中加入Ii RNA导致形成α/β/Ii复合物。即使在α/β组装过程中存在过量的Ii，也能检测到II类分子与肽的结合。这些发现表明肽可以在内质网微环境中结合α/β异二聚体，并表明由II类分子在细胞表面呈递的源自胞质蛋白的肽可能在内质网中已与HLA - DR结合。
