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A fast recoiling silk-like elastomer facilitates nanosecond nematocyst discharge.

Beckmann A, Xiao S, Müller JP, Mercadante D, Nüchter T, Kröger N, Langhojer F, Petrich W, Holstein TW, Benoit M, Gräter F, Özbek S - BMC Biol. (2015)

Bottom Line: 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 force spectroscopy.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany. Anna.beckmann@cos.uni-heidelberg.de.

ABSTRACT

Background: The discharge of the Cnidarian stinging organelle, the nematocyst, is one of the fastest processes in biology and involves volume changes of the highly pressurised (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.

Results: Here, we characterise 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 force spectroscopy. Recombinant Cnidoin showed a high tendency for spontaneous aggregation to bundles of fibrillar structures.

Conclusions: 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.

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Related in: MedlinePlus

Cumulative successful collapsing events of four disordered proteins. Each data set contains 20 independent collapse simulations along with an exponential fit (solid line) to determine the lifetime of the extended state.
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Fig6: Cumulative successful collapsing events of four disordered proteins. Each data set contains 20 independent collapse simulations along with an exponential fit (solid line) to determine the lifetime of the extended state.

Mentions: The hypothesis that the shortening of Cnidoin peptides drives the extremely fast discharge of nematocysts has been confirmed by the observation that Cnidoin is equipped with the elasticity required to drive such a discharge. Fast collapse dynamics of Cnidoin would be required given the short sub-microsecond time scale of discharge [5]. To test the collapse dynamics, highly stretched conformations of the two repetitive Cnidoin peptide units were subjected to force-quench simulations to monitor collapse dynamics in comparison to other disordered peptides, namely two silk amorphous peptides and two domain linker peptides in the von Willebrand Factor (vWF). Both are also disordered peptides but with sequence compositions similar to folded proteins (see Additional file 7: Figure S7) [17,41]. The number of trajectories in which a fully stretched peptide has reached the collapsed state is shown in Figure 6, from which the lifetime of the extended state was calculated. The Cnidoin peptide was found to have a lifetime of 5.7 ns, which is longer than that of silk (3.7 ns) and shorter than that of the vWF linker (10.5 ns). Thus, Cnidoin has a moderate collapse dynamics between the highly elastic silk protein and the vWF linker, for which an elastomeric function is unknown. The lifetime of extended mutated Cnidoin peptides lacking methionines was found to be 4.7 ns, suggesting that the large methionine side chains do not favour fast collapse. The high content of methionine residues in Cnidoin thus is likely to have a function different from enhancing collapse.Figure 6


A fast recoiling silk-like elastomer facilitates nanosecond nematocyst discharge.

Beckmann A, Xiao S, Müller JP, Mercadante D, Nüchter T, Kröger N, Langhojer F, Petrich W, Holstein TW, Benoit M, Gräter F, Özbek S - BMC Biol. (2015)

Cumulative successful collapsing events of four disordered proteins. Each data set contains 20 independent collapse simulations along with an exponential fit (solid line) to determine the lifetime of the extended state.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4321713&req=5

Fig6: Cumulative successful collapsing events of four disordered proteins. Each data set contains 20 independent collapse simulations along with an exponential fit (solid line) to determine the lifetime of the extended state.
Mentions: The hypothesis that the shortening of Cnidoin peptides drives the extremely fast discharge of nematocysts has been confirmed by the observation that Cnidoin is equipped with the elasticity required to drive such a discharge. Fast collapse dynamics of Cnidoin would be required given the short sub-microsecond time scale of discharge [5]. To test the collapse dynamics, highly stretched conformations of the two repetitive Cnidoin peptide units were subjected to force-quench simulations to monitor collapse dynamics in comparison to other disordered peptides, namely two silk amorphous peptides and two domain linker peptides in the von Willebrand Factor (vWF). Both are also disordered peptides but with sequence compositions similar to folded proteins (see Additional file 7: Figure S7) [17,41]. The number of trajectories in which a fully stretched peptide has reached the collapsed state is shown in Figure 6, from which the lifetime of the extended state was calculated. The Cnidoin peptide was found to have a lifetime of 5.7 ns, which is longer than that of silk (3.7 ns) and shorter than that of the vWF linker (10.5 ns). Thus, Cnidoin has a moderate collapse dynamics between the highly elastic silk protein and the vWF linker, for which an elastomeric function is unknown. The lifetime of extended mutated Cnidoin peptides lacking methionines was found to be 4.7 ns, suggesting that the large methionine side chains do not favour fast collapse. The high content of methionine residues in Cnidoin thus is likely to have a function different from enhancing collapse.Figure 6

Bottom Line: 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 force spectroscopy.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Evolution and Genomics, University of Heidelberg, Centre for Organismal Studies, Im Neuenheimer Feld 329, 69120, Heidelberg, Germany. Anna.beckmann@cos.uni-heidelberg.de.

ABSTRACT

Background: The discharge of the Cnidarian stinging organelle, the nematocyst, is one of the fastest processes in biology and involves volume changes of the highly pressurised (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.

Results: Here, we characterise 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 force spectroscopy. Recombinant Cnidoin showed a high tendency for spontaneous aggregation to bundles of fibrillar structures.

Conclusions: 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.

Show MeSH
Related in: MedlinePlus