Robinson R A, Lee D R
Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO 65212, USA.
J Immunol. 1996 Jun 1;156(11):4266-73.
To determine how peptides that lack a consensus binding motif interact with class I molecules, we have studied the binding of the tumor-associated tum- P91A 14-22 (tum-) peptide to Ld. Previously, a proline at position 2 (P2) and a hydrophobic residue at P9 had been defined as anchors for Ld ligands. However, the tum- peptide lacks the P2 proline anchor. To compare how peptides with and without the P2 proline anchor bind to Ld, we analyzed the binding of monosubstituted analogues of the murine cytomegalovirus (MCMV) pp89 168-176 and the tum- peptides to Ld. As expected, the binding of both peptides was inhibited by substitutions at P9, the carboxyl-terminal anchor. As also predicted, the MCMV peptide was found to be dependent upon its P2 proline for binding to Ld. By contrast, the binding of the tum- peptide to Ld is dependent primarily on a P8 aspartate residue. Interestingly, the p2Ca peptide that is immunodominant in allorecognition of Ld also lacks the P2 proline anchor and has been shown to depend on residues near the carboxyl terminus for binding to Ld. Furthermore, both the p2Ca and the tum- peptides can bind to Ld as octamers. These combined studies suggest that there are at least two alternative manners by which peptides can bind to Ld. Although most Ld ligands bind using a P2 proline anchor, the tum- and p2Ca peptides bind using alternative anchors in the carboxyl-terminal region.
为了确定缺乏共有结合基序的肽如何与I类分子相互作用，我们研究了肿瘤相关的tum-P91A 14-22（tum-）肽与Ld的结合。此前，已确定第2位（P2）的脯氨酸和第9位的疏水残基为Ld配体的锚定残基。然而，tum-肽缺乏P2脯氨酸锚定残基。为了比较有和没有P2脯氨酸锚定残基的肽如何与Ld结合，我们分析了小鼠巨细胞病毒（MCMV）pp89 168-176的单取代类似物和tum-肽与Ld的结合情况。正如预期的那样，两种肽的结合都受到羧基末端锚定残基P9处取代的抑制。同样如预测的那样，发现MCMV肽与Ld结合依赖于其P2脯氨酸。相比之下，tum-肽与Ld的结合主要依赖于P8天冬氨酸残基。有趣的是，在Ld的同种异体识别中具有免疫显性的p2Ca肽也缺乏P2脯氨酸锚定残基，并且已显示其与Ld结合依赖于羧基末端附近的残基。此外，p2Ca和tum-肽都可以以八聚体形式与Ld结合。这些综合研究表明，肽与Ld结合至少有两种不同方式。虽然大多数Ld配体使用P2脯氨酸锚定残基结合，但tum-和p2Ca肽使用羧基末端区域的替代锚定残基结合。
