|Anna Beckmann, Senbo Xiao, Jochen P Müller, Davide Mercadante, Timm Nüchter, Niels Kröger, Florian Langhojer, Wolfgang Petrich, Thomas W. Holstein, Martin Benoit, Frauke Gräter, Suat Özbek
|A fast recoiling silk-like elastomer facilitates nanosecond nematocyst discharge
|Hydra, Nematocyst, Elastomer, Molecular Dynamics, Single Molecule Force Spectroscopy
|BMC Biology (2015), 13:3
The discharge of the Cnidarian stinging organelle, the nematocyst, is one of the fastest processes in biology and involves volume changes of the highly pressurized (150 bar) capsule of up to 50%. Hitherto the molecular basis for the unusual biomechanical properties of nematocysts has been elusive, as their structure was mainly defined as a stress-resistant collagenous matrix.
Here, we characterize Cnidoin, a novel elastic protein identified as a structural component of Hydra nematocysts. Cnidoin is expressed in nematocytes of all types and immunostainings revealed incorporation into capsule walls and tubules concomitant with minicollagens. Similar to spider silk proteins, to which it is related at sequence level, Cnidoin possesses high elasticity and fast coiling propensity as predicted by Molecular Dynamics simulations and quantified by AFM force spectroscopy. Recombinant Cnidoin showed high tendency for spontaneous aggregation to bundles of fibrillar structures.
Cnidoin represents the molecular factor involved in kinetic energy storage and release during the ultra-fast nematocyst discharge. Furthermore, it implies an early evolutionary origin of protein elastomers in basal metazoans.