Entomology Research Today is a free monthly online journal that collates and summarizes the latest research about Entomology, including details on insects, parasites, diseases.

Fifty years later: the sequence, structure and function of lacewing cross-beta silk.

Weisman S, Okada S, Mudie ST, Huson MG, Trueman HE, Sriskantha A, Haritos VS, Sutherland TD

CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia.

Classic studies of protein structure in the 1950s and 1960s demonstrated that green lacewing egg stalk silk possesses a rare native cross-beta sheet conformation. We have identified and sequenced the silk genes expressed by adult females of a green lacewing species. The two encoded silk proteins are 109 and 67 kDa in size and rich in serine, glycine and alanine. Over 70% of each protein sequence consists of highly repetitive regions with 16-residue periodicity. The repetitive sequences can be fitted to an elegant cross-beta sheet structural model with protein chains folded into regular 8-residue long beta strands. This model is supported by wide-angle X-ray scattering data and tensile testing from both our work and the original papers. We suggest that the silk proteins assemble into stacked beta sheet crystallites bound together by a network of cystine cross-links. This hierarchical structure gives the lacewing silk high lateral stiffness nearly threefold that of silkworm silk, enabling the egg stalks to effectively suspend eggs and protect them from predators.

Published 30 October 2009 in J Struct Biol, 168(3): 467-75.
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