Marusina K, Reid G, Gabathuler R, Jefferies W, Monaco J J
Howard Hughes Medical Institute, Department of Molecular Genetics, University of Cincinnati, Ohio 45267-0524, USA.
Biochemistry. 1997 Jan 28;36(4):856-63. doi: 10.1021/bi9619738.
Most major histocompatibility complex (MHC) class I-binding peptides are translocated by TAP heterodimers, but some enter the ER lumen by alternative pathways. To further define mechanisms of peptide handling, we developed a system for the analysis of peptide-binding components in the ER membrane and lumen using iodinated cross-linkable peptide derivatives. Here we demonstrate that at least three proteins bind peptides in the ER lumen. Peptide cross-linking to these lumenal proteins can be used as an alternative method to monitor peptide transport. TAP and one other protein bind peptides on the cytoplasmic face of the ER. The presence of multiple peptide-binding proteins necessitates caution in interpreting traditional peptide-binding and transport assays. Finally, we demonstrate sequence-specific peptide transport in TAP-deficient cells transfected with only rat TAP1.
大多数主要组织相容性复合体（MHC）I类结合肽由TAP异二聚体转运，但有些通过替代途径进入内质网腔。为了进一步确定肽处理机制，我们开发了一种系统，用于使用碘化可交联肽衍生物分析内质网膜和腔中的肽结合成分。在此我们证明，至少有三种蛋白质在内质网腔中结合肽。肽与这些腔蛋白的交联可作为监测肽转运的替代方法。TAP和另一种蛋白质在内质网的胞质面结合肽。多种肽结合蛋白的存在使得在解释传统的肽结合和转运测定时需要谨慎。最后，我们证明了在仅转染大鼠TAP1的TAP缺陷细胞中存在序列特异性肽转运。
