Spider proteins

Topic Spider Proteins Sci Links code HW4132... 

Secondary Structure. The silkworm cocoon and spider dragline silks are characterized as an antiparaHel P-pleated sheet wherein the polymer chain axis is parallel to the fiber axis. Other silks are known to form a-hehcal (bees, wasps, ants) or cross- P-sheet (many insects) stmctures. The cross-P-sheets are characterized by a polymer chain axis perpendicular to the fiber axis and a higher serine content. Most silks assume a range of different secondary stmctures during processing from soluble protein in the glands to insoluble spun fibers. 

An elegant NMR experiment by the group of Lynn Jelinski at Cornell University has established that at least part of the microcrystals is built up from the polyalanine repeats in the protein chains. These experiments, which were made on C-enriched proteins produced by feeding the spiders C-labeled alanine, showed that there were two populations of alanine side chains, one ordered and oriented perpendicular to the fiber axis and a second less ordered. Jelinski s interpretation is that parts of the polyalanine sequences are incorporated as p strands in the microcrystals with an orientation parallel to the fiber axis. Whether or not the Gly-Gly-X repeats also form P strands in the microcrystals remains an open question. 

Xu, M., Lewis, R.V. Structure of a protein superfiber spider dragline silk. Proc. Natl. Acad. Sci. USA 87 7120-7124, 1990. 

This combination of strength and flexibility derives from the eomposite nature of spider silk. As keratin protein is extruded from... 

FIGURE 19.22 The protein produced by spiders to make a web is a form of silk that can be exceptionally strong. 

The structures of some natural protein-based materials, such as silk and wool, result in strong, tough fibers. Spiders and silkworms use proteins as a structural material of remarkable strength (Fig. 19.22). Chemists are duplicating nature by making artificial spider silk (Fig. 19.23), which is one of the strongest fibers known. 

Hayashi C. and Lewis R., Molecular architecture and evolution of a modular spider silk protein gene. Science, 287, 1477, 2000. 

Hayash C.I., Shipley N., and Lewis R., Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins, Int. J. Biol. Macromol., 24, 271, 1999. 

Hayashi C.Y. and Lewis R.V., Spider flagelUfotm silk Lessons in protein design, gene structure, and molecular evolution, BioEssays, 23, 750, 2001. 

Parkhe AD, Seeley SK, Gardner K (1997) Structural studies of spider silk proteins in the fiber. J Mol Recognit 10 1-6... 

Chemists teamed the basic composition of siik many years ago, but the reasons why this macromoiecuie is so strong, yet fiexibie, are stiii not fuiiy understood. Recent studies indicate that the secret ties in the way the chains of this protein nestie together. Current research efforts focus on using techniques of genetic engineering to repiicate naturai spider siik on a usefui scaie. 

Production of Spider Silk Proteins in Transgenic Tobacco and Potato... 

Tab.11.1 Spider silk proteins MaSpI, MaSpll and Flag from Nephila davipes.

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