de la Arada Igor, Julien Jean-Philippe, de la Torre Beatriz G, Huarte Nerea, Andreu David, Pai Emil F, Arrondo José L R, Nieva José L
Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain.
J Phys Chem B. 2009 Oct 15;113(41):13626-37. doi: 10.1021/jp905965h.
The HIV-1 gp41 epitope recognized by the broadly neutralizing 2F5 antibody has focused much attention as a suitable target in the design of peptide immunogens. Peptides mimicking the linear 2F5 epitope (2F5ep) are however intrinsically disordered, while the structural constraints existing in the cognate gp41 native structure recognized by the antibody are presently unknown. In recent reports, we have shown that core residues of the amino-terminal fusion peptide (FP) increase MAb2F5 affinity. Here, we have inferred the sequence-specific structural constraints imposed by the FP residues on the 2F5 epitope from the comparison of two hybrid peptides: HybK3, which connects through a flexible tether residues derived from 2F5ep and FP sequences, and scrHybK3, combining 2F5ep and an FP sequence with the conserved core scrambled. Circular dichroism, conventional and two-dimensional correlation infrared spectroscopy, and X-ray diffraction studies revealed specific structural features that were dependent on the exact FP sequence, namely, (i) the production with moderate low polarity of an intermediate folded structure enriched in beta-turns and alpha-helix; (ii) the existence in this intermediate of a thermotropic conformational transition taking place at ca. 18-20 degrees C, consistent with the conversion of 3(10)-helices into beta-turn conformers; and (iii) the presence of a C-terminal alpha-helix in crystals of Fab'-peptide complexes. Those features support the existence of native-like tertiary interactions between FP and 2F5 epitope residues, which might be important to recreate when developing an effective AIDS peptide vaccine.
被广泛中和的2F5抗体识别的HIV-1 gp41表位作为肽免疫原设计中的合适靶点备受关注。然而，模拟线性2F5表位（2F5ep）的肽本质上是无序的，而该抗体识别的同源gp41天然结构中存在的结构限制目前尚不清楚。在最近的报道中，我们已经表明氨基末端融合肽（FP）的核心残基增加了单克隆抗体2F5的亲和力。在这里，我们通过比较两种杂合肽推断了FP残基对2F5表位施加的序列特异性结构限制：HybK3，它通过柔性连接子连接源自2F5ep和FP序列的残基；以及scrHybK3，它将2F5ep和一个核心保守序列被打乱的FP序列结合在一起。圆二色性、常规和二维相关红外光谱以及X射线衍射研究揭示了特定的结构特征，这些特征取决于确切的FP序列，即：（i）产生具有适度低极性的富含β-转角和α-螺旋的中间折叠结构；（ii）在该中间体中存在约18 - 20℃发生的热致构象转变，这与3（10）-螺旋向β-转角构象体的转变一致；以及（iii）在Fab'-肽复合物晶体中存在C末端α-螺旋。这些特征支持了FP和2F5表位残基之间存在类似天然的三级相互作用，这在开发有效的艾滋病肽疫苗时可能很重要。
