Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
J Am Chem Soc. 2013 Apr 24;135(16):6014-7. doi: 10.1021/ja402187t. Epub 2013 Apr 15.
Hydroxyproline plays a major role in stabilizing collagenous domains in eukaryotic organisms. Lack of this modification is associated with significant lowering in the thermal stability of the collagen triple helix and may also affect fibrillogenesis and folding of the peptide chains. In contrast, even though bacterial collagens lack hydroxyproline, their thermal stability is comparable to that of fibrillar collagen. This has been attributed to the high frequency of charged amino acids found in bacterial collagen. Here we report a thermally stable hydroxyproline-free ABC heterotrimeric collagen mimetic system composed of decapositive and decanegative peptides and a zwitterionic peptide. None of the peptides contain hydroxyproline, and furthermore the zwitterionic peptide does not even contain proline. The heterotrimer is electrostatically stabilized via multiple interpeptide lysine-aspartate and lysine-glutamate salt bridges and maintains good thermal stability with a melting temperature of 37 °C. The ternary peptide mixture also populates a single composition ABC heterotrimer as confirmed by circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. This system illustrates the power of axial salt bridges to direct and stabilize the self-assembly of a triple helix and may be useful in analogous designs in expression systems where the incorporation of hydroxyproline is challenging.
羟脯氨酸在稳定真核生物胶原结构域中起着重要作用。缺乏这种修饰会显著降低胶原三螺旋的热稳定性，也可能影响肽链的原纤维形成和折叠。相比之下，尽管细菌胶原缺乏羟脯氨酸，但它们的热稳定性与纤维状胶原相当。这归因于细菌胶原中存在大量带电荷的氨基酸。本文报道了一种由带正电的十肽和带负电的十肽以及两性离子肽组成的热稳定的、无羟脯氨酸的 ABC 三聚体胶原模拟系统。这些肽中均不含羟脯氨酸，而且两性离子肽甚至不含脯氨酸。通过多个肽间赖氨酸-天冬氨酸和赖氨酸-谷氨酸盐桥的静电作用稳定三聚体，其具有良好的热稳定性，熔点为 37°C。圆二色性（CD）和核磁共振（NMR）光谱证实，三元肽混合物还可形成单一组成的 ABC 三聚体。该系统说明了轴向盐桥在指导和稳定三聚体自组装方面的强大功能，在表达系统中可能具有类似的设计意义，在这些系统中，羟脯氨酸的掺入具有挑战性。
