期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 405, 期 1, 页码 238-253出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2010.10.052
关键词
Raman spectromicroscopy; spider silk proteins; spinning dope; secondary structure; sericigene glands
资金
- Canadian Foundation for Innovation
- Natural Sciences and Engineering Research Council of Canada
- Fonds Quebecois de Recherche sur la Nature et les Technologies
Spiders that spin orb webs secrete seven types of silk. Although the spinning process of the dragline thread is beginning to be understood, the molecular events that occur in spiders' opisthosomal glands, which produce the other fibers, are unknown due to a lack of data regarding their initial and final structures. Taking advantage of the efficiency of Raman spectromicroscopy in investigating micrometer-sized biological samples, we have determined the secondary structure of proteins in the complete set of glands of the orb-weaving spider Nephila clavipes. The major and minor ampullate silks in the sac of their glands have identical secondary structures typical of natively unfolded proteins. Spidroins are converted into fibers containing highly oriented beta-sheets. The capture spiral represents a distinct structural singleton. The proteins are highly disordered prior to spinning and undergo no molecular change or alignment upon spinning. The cylindrical, aciniform, and piriform proteins are folded in their initial state with a predominance of alpha-helices, but whereas the cylindrical gland forms a fiber similar to the major ampullate thread, the aciniform and piriform glands produce fibers dominated by moderately oriented beta-sheets and alpha-helices. The conformation of the proteins before spinning is related to intrinsic characteristics of their primary structure. Proteins that are unfolded in the gland have repeat sequences composed of submotifs and display no sequence regions with aggregation propensity. By contrast, the folded proteins have neither submotifs nor aggregation-prone sequence regions. Taken together, the Raman data show a remarkable diversity of molecular transformations occurring upon spinning. (c) 2010 Elsevier Ltd. All rights reserved.
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