Core sequence of PAPf39 amyloid fibrils and mechanism of pH-dependent fibril formation: the role of monomer conformation.
Core sequence of PAPf39 amyloid fibrils and mechanism of pH-dependent fibril formation: the role of monomer conformation.
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DOI：
10.1021/bi301406d
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发表时间：
2012-12-21
期刊：
影响因子：
2.9
通讯作者：
Makhatadze GI
中科院分区：
文献类型：
--
作者：
French KC;Makhatadze GI
PAPf 39是来自人前列腺酸性磷酸酶的39个残基的肽片段，已被证明在精液中形成淀粉样纤维（SEVI），其将HIV感染性增加多达5个数量级。使用HDXMS和蛋白酶保护测定来鉴定PAPf 39原纤维核心的序列。中心和C-末端区域受到高度保护，不受HDX和蛋白水解切割的影响，因此是原纤维核心的一部分。相反，N-末端区域不受HDX和蛋白水解切割的保护，这表明它是暴露的，而不是纤维核心的一部分。使用两种N末端截短变体PAPf 39 Δ1-8和PAPf 39 Δ1-13测试了这一发现。这两种变体在中性pH下形成淀粉样蛋白原纤维。然而，这些变体显示出与PAPf 39相比原纤维形成的显著不同的pH依赖性。PAPf 39原纤维可以在pH 7.7下形成，但不能在pH 5.5和pH 2.5下形成，而两种N-末端截短的变体都可以在这些pH值下形成原纤维。因此，N-末端区域不是原纤维形成所必需的，但调节PAPf 39原纤维形成的pH依赖性。PAPf 39 Δ1-8和PAPf 39 Δ1-13能够在中性pH下接种PAPf 39原纤维形成，表明这些变体在结构上与PAPf 39相容。然而，在低pH下，在截短的变体和PAPf 39之间没有发生混合原纤维形成。这表明pH影响PAPf 39单体构象集合，这是由远紫外CD光谱支持的。一个概念模型描述的pH依赖性的PAPf 39聚集的建议，并提供了潜在的生物学意义。
PAPf39, a 39 residue peptide fragment from human prostatic acidic phosphatase, has been shown to form amyloid fibrils in semen (SEVI), which increase HIV infectivity by up to five orders of magnitude. The sequence of the PAPf39 fibrillar core was identified using HDXMS and protease protection assays. The central and C-terminal regions are highly protected from HDX and proteolytic cleavage and, thus, are part of the fibrillar core. Conversely, the N-terminal region is unprotected from HDX and proteolytic cleavage, suggesting that it is exposed and not part of the fibrillar core. This finding was tested using two N-terminal truncated variants, PAPf39Δ1-8 and PAPf39Δ1-13. Both variants formed amyloid fibrils at neutral pH. However, these variants showed a markedly different pH dependence of fibril formation than PAPf39. PAPf39 fibrils can form at pH 7.7, but not at pH 5.5 and pH 2.5, while both N-terminal truncated variants can form fibrils at these pH values. Thus, the N-terminal region is not necessary for fibril formation but modulates the pH dependence of PAPf39 fibril formation. PAPf39Δ1-8 and PAPf39Δ1-13 are capable of seeding PAPf39 fibril formation at neutral pH, suggesting that these variants are structurally compatible with PAPf39. Yet, no mixed fibril formation occurs between the truncated variants and PAPf39 at low pH. This suggests that pH affects the PAPf39 monomer conformational ensemble, which is supported by far-UV CD spectroscopy. A conceptual model describing the pH dependence of PAPf39 aggregation is proposed and provides potential biological implications.
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影响因子：
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作者：
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