posted 26. January 2006 22:53                    

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Ankyrin repeats are an amino-acid motif believed to function in protein recognition; they are present in tandem copies in diverse proteins in nearly all phyla1. Ankyrin repeats contain antiparallel alpha-helices that can stack to form a superhelical spiral2. Visual inspection of the extrapolated structure of 24 ankyrin-R repeats2 indicates the possibility of spring-like behaviour of the putative superhelix. Moreover, stacks of 17–29 ankyrin repeats in the cytoplasmic domains of transient receptor potential (TRP) channels have been identified as candidates for a spring that gates mechanoreceptors in hair cells as well as in Drosophila bristles3, 4, 5. Here we report that tandem ankyrin repeats exhibit tertiary-structure-based elasticity and behave as a linear and fully reversible spring in single-molecule measurements by atomic force microscopy. We also observe an unexpected ability of unfolded repeats to generate force during refolding, and report the first direct measurement of the refolding force of a protein domain. Thus, we show that one of the most common amino-acid motifs has spring properties that could be important in mechanotransduction and in the design of nanodevices.

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Protein “Nanosprings” most resilient in Nature
A component of many proteins has been found to constitute one of the most powerful and resilient molecular “springs” in nature, researchers have discovered. The engineers and biologists from Duke University and the Howard Hughes Medical Institute say their discovery could lead to a new understanding of mechanical processes within the living cell. The discovery also could provide potent nanoscale “shock absorbers” or “gate-opening springs” in tiny nanomachines.

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"After repeated stretching, the molecules immediately refold themselves, retaining their shape and strength."
"The fully extended molecules not only bounce back to their original shape in real time, but they also generate force in the process of this rapid refolding - something that had never been seen before."

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