Premium
In vivo structures of an intact type VI secretion system revealed by electron cryotomography
Author(s) -
Chang YiWei,
Rettberg Lee A,
Ortega Davi R,
Jensen Grant J
Publication year - 2017
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.15252/embr.201744072
Subject(s) - periplasmic space , cytoplasm , secretion , bacteriophage , cell envelope , microbiology and biotechnology , type vi secretion system , biology , inner membrane , bacterial outer membrane , extracellular , biophysics , lysis , biochemistry , virulence , escherichia coli , mitochondrion , gene
The type VI secretion system (T6 SS ) is a versatile molecular weapon used by many bacteria against eukaryotic hosts or prokaryotic competitors. It consists of a cytoplasmic bacteriophage tail‐like structure anchored in the bacterial cell envelope via a cytoplasmic baseplate and a periplasmic membrane complex. Rapid contraction of the sheath in the bacteriophage tail‐like structure propels an inner tube/spike complex through the target cell envelope to deliver effectors. While structures of purified contracted sheath and purified membrane complex have been solved, because sheaths contract upon cell lysis and purification, no structure is available for the extended sheath. Structural information about the baseplate is also lacking. Here, we use electron cryotomography to directly visualize intact T6 SS structures inside Myxococcus xanthus cells. Using sub‐tomogram averaging, we resolve the structure of the extended sheath and membrane‐associated components including the baseplate. Moreover, we identify novel extracellular bacteriophage tail fiber‐like antennae. These results provide new structural insights into how the extended sheath prevents premature disassembly and how this sophisticated machine may recognize targets.