Action of a minimal contractile bactericidal nanomachine

By: Peng Ge, Dean Scholl, Nikolai S. Prokhorov, Jaycob Avaylon, Mikhail M. Shneider, Christopher Browning, Sergey A. Buth, Michel Plattner, Urmi Chakraborty, Ke Ding, Petr G. Leiman, Jeff F. Miller & Z. Hong Zhou | Source: Nature

R-type bacteriocins are minimal contractile nanomachines that hold promise as precision antibiotics1,2,3,4. Each bactericidal complex uses a collar to bridge a hollow tube with a contractile sheath loaded in a metastable state by a baseplate scaffold1,2. Fine-tuning of such nucleic acid-free protein machines for precision medicine calls for an atomic description of the entire complex and contraction mechanism, which is not available from baseplate structures of the (DNA-containing) T4 bacteriophage5. Here we report the atomic model of the complete R2 pyocin in its pre-contraction and post-contraction states, each containing 384 subunits of 11 unique atomic models of 10 gene products. Comparison of these structures suggests the following sequence of events during pyocin contraction: tail fibres trigger lateral dissociation of baseplate triplexes; the dissociation then initiates a cascade of events leading to sheath contraction; and this contraction converts chemical energy into mechanical force to drive the iron-tipped tube across the bacterial cell surface, killing the bacterium.