BACKGROUND Many β-strands are not flat but bend and/or twist. However, although almost all β-strands have a twist, not all have a bend, suggesting that the underlying force(s) driving β-strand bending is distinct from that for the twist. We, therefore, investigated the physical origin(s) of β-strand bends. METHODS We calculated rotation, twist and bend angles for a four-residue short frame. Fixed-length fragments consisting of six residues found in three consecutive short frames were used to evaluate the twist and bend angles of full-length β-strands. RESULTS We calculated and statistically analyzed the twist and bend angles of β-strands found in globular proteins with known three-dimensional structures. The results show that full-length β-strand bend angles are related to the nearby aromatic residue content, whereas local bend angles are related to the nearby aliphatic residue content. Furthermore, it appears that β-strands bend to maximize their hydrophobic contacts with an abutting hydrophobic surface or to form a hydrophobic side-chain cluster when an abutting hydrophobic surface is absent. CONCLUSIONS We conclude that the dominant driving force for full-length β-strand bends is the hydrophobic interaction involving aromatic residues, whereas that for local β-strand bends is the hydrophobic interaction involving aliphatic residues.

中文翻译：

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球形蛋白中β链弯曲的起源。

背景技术许多β链不是平坦的而是弯曲和/或扭曲的。然而，尽管几乎所有的β链都具有扭曲，但并非全部都具有弯曲，这表明驱动β链弯曲的基本力与扭曲的力不同。因此，我们研究了β链弯曲的物理起源。方法我们计算了四残基短框架的旋转角度，扭曲角度和弯曲角度。使用在三个连续的短帧中发现的由六个残基组成的定长片段来评估全长β链的扭曲和弯曲角度。结果我们计算并统计分析了具有已知三维结构的球形蛋白质中发现的β链的扭曲和弯曲角度。结果表明，全长β链弯曲角与附近的芳族残基含量有关，而局部弯曲角与附近的脂肪族残基含量有关。此外，当不存在邻接的疏水性表面时，似乎β链弯曲以最大化其与邻接的疏水性表面的疏水性接触或形成疏水性侧链簇。结论我们得出结论，全长β链弯曲的主要驱动力是涉及芳香族残基的疏水相互作用，而局部β链弯曲的主要驱动力是涉及脂肪族残基的疏水相互作用。