DOI: 10.1101/470229Nov 15, 2018Paper

The double tubular contractile structure of the type VI secretion system displays striking flexibility and elasticity

BioRxiv : the Preprint Server for Biology
Maria Silvina StietzTao G Dong

Abstract

The double tubular structure of the type VI secretion system (T6SS) is considered as one of the longest straight and rigid intracellular structures in bacterial cells. Contraction of the T6SS outer sheath occurs almost instantly and releases sufficient power to inject the inner needle-like Hcp tube and its associated effectors into target bacterial cells through piercing the stiff cell envelope. The molecular mechanism triggering T6SS contraction remains elusive. Here we report that the double tubular T6SS structure is strikingly flexible and elastic, forming U-, circular-, or S- shapes while maintaining functional for contraction and substrate delivery. We show that physical contact with cytoplasmic membrane induced a range of T6SS structure deformation, but the resultant mechanical pressing force on the T6SS baseplate did not trigger contraction. Our results also reveal a stalling intermediate stage of sheath-tube extension following which the structure contracts or resumes to extend. These observations suggest that the recruitment equilibrium of sheath-tube precursors to the extending structure is key to stability/contraction and lead us to propose a model of T6SS contraction, termed ESCAPE (extension-stall-contraction and p...Continue Reading

Related Concepts

Plasma Membrane
Needle Device
Biomedical Tube Device
Intracellular
Shapes
Extent
Tubulo-reticular Structure
Cell Envelope
Structure
Piercing Procedure

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