Reinvestigation of the proposed folding and self-association of the Neuropeptide Head Activator.
Reinvestigation of the proposed folding and self-association of the Neuropeptide Head Activator.
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重新研究神经肽头激活剂的拟议折叠和自缔合。
DOI：
10.1110/ps.0232103
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Gellman,SamuelH
中科院分区：
文献类型：
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作者：
Lai,JonathanR;Gellman,SamuelH
神经肽头部激活剂 (HA)、pGlu-Pro-Pro-Gly-Gly-Ser-Lys-Val-Ile-Leu-Phe（pGlu 是焦谷氨酸）参与淡水腔肠动物 Hydra attenuata 的头部特异性生长和分化过程。相同序列的肽也已从人类和牛的下丘脑等高等生物组织中分离出来。分子筛色谱的早期研究表明，HA 以高亲和力 (Kd≈ 1 nM) 进行二聚化。这种二聚化被认为是通过每个 HA 分子的 Lys7-Phe11 片段之间形成反平行 β 片层而发生的。我们对合成 HA 进行了生物物理学研究，以深入了解其结构和聚集趋势。我们通过分析超速离心发现 HA 在低毫摩尔浓度下是单体。 1 H-NMR研究表明HA在溶液中没有采取任何显着的二级结构。我们发现没有 NOE 支持所提出的二聚体结构。我们通过设计肽来探究 Lys7-Phe11 片段形成反平行 β 折叠的倾向，其中两个此类片段通过双残基连接子连接。这些肽旨在形成稳定的 β-发夹结构，具有模拟所提出的 HA 二聚体界面的跨链相互作用。我们发现，当通过高度 β-发夹促进-Pro-Gly 转角连接时，HA 衍生片段可能会被诱导形成分子内 β-折叠，尽管这种作用很弱，但当通过更灵活的 Gly-Gly 单元连接时则不会。这些发现表明，HA 二聚化的假设模式和分子形成具有高亲和力的离散聚集体的拟议倾向是不正确的。
The Neuropeptide Head Activator (HA), pGlu‐Pro‐Pro‐Gly‐Gly‐Ser‐Lys‐Val‐Ile‐Leu‐Phe (pGlu is pyroglutamic acid), is involved in head‐specific growth and differentiation processes in the freshwater coelenterateHydra attenuata. Peptides of identical sequence have also been isolated from higher‐organism tissues such as human and bovine hypothalamus. Early studies by molecular sieve chromatography suggested that HA dimerizes with high affinity (Kd≈ 1 nM). This dimerization was proposed to occur via antiparallel β‐sheet formation between the Lys7‐Phe11segments in each HA molecule. We conducted biophysical studies on synthetic HA in order to gain insight into its structure and aggregation tendencies. We found by analytical ultracentrifugation that HA is monomeric at low millimolar concentrations. Studies by1H‐NMR revealed that HA did not adopt any significant secondary structure in solution. We found no NOEs that would support the proposed dimer structure. We probed the propensity of the Lys7‐Phe11fragment to form antiparallel β‐sheet by designing peptides in which two such fragments are joined by a two‐residue linker. These peptides were intended to form stable β‐hairpin structures with cross‐strand interactions that mimic those of the proposed HA dimer interface. We found that the HA‐derived fragments may be induced to form intramolecular β‐sheet, albeit only weakly, when linked by the highly β‐hairpin‐promotingd‐Pro‐Gly turn, but not when linked by the more flexible Gly‐Gly unit. These findings suggest that the postulated mode of HA dimerization and the proposed propensity of the molecule to form discrete aggregates with high affinity are incorrect.