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Native-sized recombinant spider silk protein produced in metabolically engineered Escherichia coli results in a strong fiber
Xiao-Xia Xia, Zhi-Gang Qian, Chang Seok Ki, Young Hwan Park, David L. Kaplan, Sang Yup Lee and Arnold L. Demain
Proceedings of the National Academy of Sciences of the United States of America
Vol. 107, No. 32 (August 10, 2010), pp. 14059-14063
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25708855
Page Count: 5
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Spider dragline silk is a remarkably strong fiber that makes it attractive for numerous applications. Much has thus been done to make similar fibers by biomimic spinning of recombinant dragline silk proteins. However, success is limited in part due to the inability to successfully express native-sized recombinant silk proteins (250–320 kDa). Here we show that a 284.9 kDa recombinant protein of the spider Nephila clavipes is produced and spun into a fiber displaying mechanical properties comparable to those of the native silk. The native-sized protein, predominantly rich in glycine (44.9%), was favorably expressed in metabolically engineered Escherichia coli within which the glycyl-tRNA pool was elevated. We also found that the recombinant proteins of lower molecular weight versions yielded inferior fiber properties. The results provide insight into evolution of silk protein size related to mechanical performance, and also clarify why spinning lower molecular weight proteins does not recapitulate the properties of native fibers. Furthermore, the silk expression, purification, and spinning platform established here should be useful for sustainable production of natural quality dragline silk, potentially enabling broader applications.
Proceedings of the National Academy of Sciences of the United States of America © 2010 National Academy of Sciences