Energetics and cooperativity of the hydrogen bonding and anchor interactions that bind peptides to MHC class II protein
Energetics and cooperativity of the hydrogen bonding and anchor interactions that bind peptides to MHC class II protein
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DOI：
10.1016/j.jmb.2005.04.069
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发表时间：
2005-07-01
影响因子：
5.6
通讯作者：
Beeson, C
中科院分区：
文献类型：
--
作者：
McFarland, BJ;Katz, JF;Beeson, C
主要组织相容性复合物II类（MHC II）蛋白和肽配体之间的相互作用的复杂性已通过结构研究和晶体学表征揭示。肽通过与MHC II口袋的侧链“锚”相互作用和与肽骨架的大量遗传保守氢键结合。在这里，我们定量研究这些相互作用的动力学层次。我们目前的结果详细说明了解离速率的肽锚残基的单侧链突变的影响，利用两个I-A（d）-限制性肽，其中一个具有已知的晶体结构，和24个天然和非天然氨基酸突变体的这些肽的变体。我们发现N-末端P1、P4和P6锚口袋相互作用对结合稳定性有重要贡献。我们还研究了这些肽与四种I-A（d）MHC II蛋白的相互作用，每种蛋白都突变以破坏与肽骨架的保守氢键。这些复合物表现出动力学行为，表明结合能不成比例地投资在肽N末端附近的骨架氢键。然后，我们评估同时修改两个锚和氢键相互作用的影响。对71个双突变体循环的定量分析表明，锚残基相互作用和氢键之间几乎没有明显的协同性，即使它们直接相邻（< 5埃）。(c)2005爱思唯尔有限公司保留所有权利。
The complexity of the interaction between major histocompatibility complex class II (MHC II) proteins and peptide ligands has been revealed through structural studies and crystallographic characterization. Peptides bind through side-chain "anchor" interactions with MHC II pockets and an extensive array of genetically conserved hydrogen bonds to the peptide backbone. Here we quantitatively investigate the kinetic hierarchy of these interactions. We present results detailing the impact of single side-chain mutations of peptide anchor residues on dissociation rates, utilizing two I-A(d)-restricted peptides, one of which has a known crystal structure, and 24 natural and non-natural amino acid mutant variants of these peptides. We find that the N-terminal P1, P4 and P6 anchor-pocket interactions can make significant contributions to binding stability. We also investigate the interactions of these peptides with four I-A(d) MHC II proteins, each mutated to disrupt conserved hydrogen bonds to the peptide backbone. These complexes exhibit kinetic behavior suggesting that binding energy is disproportionately invested near the peptide N terminus for backbone hydrogen bonds. We then evaluate the effects of simultaneously modifying both anchor and hydrogen bonding interactions. A quantitative analysis of 71 double mutant cycles reveals that there is little apparent cooperativity between anchor residue interactions and hydrogen bonds, even when they are directly adjacent (< 5 angstrom). (c) 2005 Elsevier Ltd. All rights reserved.