Volume 92 Issue 49 | p. 31 | Concentrates
Issue Date: December 8, 2014

Watching The Rapid, Tiny Protein Motions That Build Spider Silk

Combination of fluorescence techniques measures motions beyond the resolution limit of single-molecule spectroscopy
Department: Science & Technology | Collection: Critter Chemistry
News Channels: Biological SCENE, Materials SCENE
Keywords: spider silk, fluorescence, molecular probes, polymer chemistry
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This spider silk monomer N-terminal domain, with a tryptophan (blue spacefill structure) and fluorophore (red spacefill structure) pair, helped monitor 1-nm-scale protein motions.
Credit: J. Am. Chem. Soc.
Representation of spider silk spidroin N-terminal domain, engineered to contain tryptophan (blue spacefill) and fluorophore (red spacefill) pairs to monitor 1-nm-scale motions.
 
This spider silk monomer N-terminal domain, with a tryptophan (blue spacefill structure) and fluorophore (red spacefill structure) pair, helped monitor 1-nm-scale protein motions.
Credit: J. Am. Chem. Soc.

Spider silk’s combination of strength and biocompatibility puts chemists’ best polymers to shame. But it’s still not clear how arachnids polymerize soluble protein monomers called spidroins into silk fibers. Hannes Neuweiler of Julius Maximilians University, in Würzburg, Germany, and colleagues zeroed in on one aspect of that question: the N-terminal domain of spidroin 1, a protein region many different spider species have in common (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja508760a). This region contains a structural switch that facilitates polymerization in response to a pH change in a spider’s spinning duct. Multiple labs have studied the region with crystallography, but Neuweiler’s team wanted a technique that could provide more insight into the protein’s motions, which are too tiny for the resolution limit of single-molecule fluorescence spectroscopy. The researchers engineered tryptophan-fluorophore pairs that could follow 1-nm-scale motions in the domain and combined those probes with correlation analysis of single-molecule fluorescence fluctuations. In tests on isolated proteins, the team learned that conformational changes in the N-terminal domain occur while the protein is still in monomer form, in contrast to some prior studies that suggest association during polymerization kicks off conformation changes.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
George Kenney (Fri Dec 12 11:23:03 EST 2014)
Cool Stuff
It'd be nice to see a video of the formation of the silk thread!

George
Retired Chemist
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