The Molecular Mechanism of Spider-Silk Formation

摘要

Spider silk, one of the most remarkable biomaterials, is made of fibers whose mechanical properties exceed those of steel once the smaller density of spider silk is taken into account: A spider silk fiber spun around the earth's equator would weigh not more than 500 grams. Spider silk from Araneus diadematus spiders contains a polypeptide chain consisting of a so-called AQ repeat sequence of low complexity in its composition (A, hydrophobic polyalanine-rich motif: GPYGPGASA6GGYGPGSGQQ; Q, hydrophilic glutamine-and glycine-rich motif: (GPGQQ)4). The repeat sequence is a central part of the fiber and its role is reminiscent of the repeat sequence in collagen. Twelve AQ sequences are flanked by a secretion signal, along with non-repetitive N-and C-terminal domains, each of which is implicated in a number of different functions, including control of solubility and fiber formation.