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Assembly Characteristics and Structural Motifs in an Aquatic Insect's Biopolymer

Published online by Cambridge University Press:  15 February 2011

Steven T. Case ,
Susan E. Wellman  and
Stavros Hamodrakas
Steven T. Case
Affiliation:
The University of Mississippi Medical Center, Department of Biochemistry, 2500 North State Street, Jackson, MS 39216-4505, U.S.A.
Susan E. Wellman
Affiliation:
The University of Mississippi Medical Center, Department of Biochemistry, 2500 North State Street, Jackson, MS 39216-4505, U.S.A.
Stavros Hamodrakas
Affiliation:
The University of Athens, Department of Biochemistry, Cell and Molecular Biology and Genetics, Panepistimiopolis, Kouponia, Athens 15701, Greece
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Abstract

Secretory proteins of Chironomus tentans larvae form insoluble fibers that are spun into threads used to construct underwater feeding and pupation tubes. The physical properties of spun fibers should reflect their protein constituents.

The disassembly and reassembly of secretory protein complexes in vitro were studied by solution turbidity, electron microscopy and circular dichroism spectroscopy. Secretory proteins were able to reform complexes with a similar morphology and dichroic spectrum to that of native complexes. These complexes are stabilized by electrostatic and disulfide bonds.

cDNA and genomic cloning indicate that spIs, the 1000-kDa secretory proteins, primarily consist of alternating “constant” and “subrepeat” regions. We synthesized and purified synthetic peptides for each region and used circular dichroism and infrared spectroscopy to measure their secondary structure. Constant peptide consists of α-helix and β-turn. Subrepeat peptide consists of poly(Gly) II-type helix and β-turn.

We conclude that spIs form the fibrous backbone of a novel biopolymer with alternating α-helices and poly(Gly)II helices punctuated by β-turns. Such fibers may have unique physical properties.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 218: Symposium V – Materials Synthesis Based on Biological Processes , 1990 , 233
Copyright
Copyright © Materials Research Society 1991

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References

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