Type IV secretion machinery: molecular architecture and function.
Bacteria have evolved several secretion machineries to bring about transport of various virulence factors, nutrients, nucleic acids and cell-surface appendages that are essential for their pathogenesis. T4S (Type IV secretion) systems are versatile secretion systems found in various Gram-negative and Gram-positive bacteria and in few archaea. They are large multisubunit translocons secreting a diverse array of substrates varying in size and nature from monomeric proteins to nucleoprotein complexes. T4S systems have evolved from conjugation machineries and are implicated in antibiotic resistance gene transfer and transport of virulence factors in Legionella pneumophila causing Legionnaires' disease, Brucella suis causing brucellosis and Helicobacter pylori causing gastroduodenal diseases. The best-studied are the Agrobacterium tumefaciens VirB/D4 and the Escherichia coli plasmid pKM101 T4S systems. Recent structural advances revealing the cryo-EM (electron microscopy) structure of the core translocation assembly and high-resolution structure of the outer-membrane pore of T4S systems have made paradigm shifts in the understanding of T4S systems. The present paper reviews the advances made in biochemical and structural studies and summarizes our current understanding of the molecular architecture of this mega-assembly.
Division of Molecular Biosciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK. v.chandran@imperial.ac.uk
Vidya
V
Chandran
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D006090:Gram-Negative Bacteria / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation
D001426:Bacterial Proteins