Dong Z, Lewis R V, Middaugh C R
Department of Molecular Biology, University of Wyoming, Laramie 82071.
Arch Biochem Biophys. 1991 Jan;284(1):53-7. doi: 10.1016/0003-9861(91)90262-h.
Spider major ampullate (drag-line) silk is an extracellular fibrous protein which has impressive characteristics of strength and elasticity. This silk has been hypothesized to predominantly consist of a single protein, containing regions of antiparallel beta-sheets which are interspersed with amorphous segments responsible for its elastic properties. A rubber-like mechanism has been suggested to account for this elasticity, but the specific molecular mechanism is unknown. Using Fourier transform infrared spectroscopy (FTIR) we found evidence of either helix formation or reorientation of preexisting helices when axial tension is applied to the spider silk fiber. CD studies of a peptide derived from the silk gene repeat sequence show that it can form beta-sheets at high temperatures while alpha-helices are induced in 2,2,2-trifluoroethanol. These results suggest a possible molecular mechanism for the elasticity of spider silk fibers. It is proposed that the elastic process involves the formation and disruption of alpha-helical Ala-rich regions which are interspersed among stable beta-sheet domains.
蜘蛛大壶状腺（拖丝）丝是一种细胞外纤维蛋白，具有令人印象深刻的强度和弹性特性。据推测，这种丝主要由单一蛋白质组成，包含反平行β-折叠区域，这些区域穿插着赋予其弹性的无定形片段。有人提出一种类似橡胶的机制来解释这种弹性，但具体的分子机制尚不清楚。使用傅里叶变换红外光谱（FTIR），我们发现当对蜘蛛丝纤维施加轴向张力时，存在螺旋形成或先前存在的螺旋重新定向的证据。对源自丝基因重复序列的肽进行的圆二色性（CD）研究表明，它在高温下可形成β-折叠，而在2,2,2-三氟乙醇中会诱导形成α-螺旋。这些结果提示了蜘蛛丝纤维弹性的一种可能分子机制。有人提出弹性过程涉及穿插在稳定β-折叠结构域之间的富含丙氨酸的α-螺旋区域的形成和破坏。
