Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins

Several types of silks and silk protein coding genes have been characterize d from orb-web weaving spiders. When the protein sequences of major ampulla te, minor ampullate, and flagelliform silks from Nephila clavipes are compa red, they can be summarized as sets of shared amino acid motifs. Four of th ese motifs and their likely secondary structures are described. Each struct ural element, termed a module, is then associated with its impact on the me chanical properties of a silk fiber. In particular, correlations are drawn between an alanine-rich 'crystalline module' and tensile strength and betwe en a proline-containing 'elasticity module' and extensibility. (C) 1999 Els evier Science B.V. All rights reserved.