X-ray crystal structures of the type IVb secretion system DotB ATPases

Protein Sci. 2018 Aug;27(8):1464-1475. doi: 10.1002/pro.3439. Epub 2018 Jul 18.


Human infections by the intracellular bacterial pathogen Legionella pneumophila result in a severe form of pneumonia, the Legionnaire's disease. L. pneumophila utilizes a Type IVb secretion (T4bS) system termed "dot/icm" to secrete protein effectors to the host cytoplasm. The dot/icm system is powered at least in part by a functionally critical AAA+ ATPase, a protein called DotB, thought to belong to the VirB11 family of proteins. Here we present the crystal structure of DotB at 3.19 Å resolution, in its hexameric form. We observe that DotB is in fact a structural intermediate between VirB11 and PilT family proteins, with a PAS-like N-terminal domain coupled to a RecA-like C-terminal domain. It also shares critical structural elements only found in PilT. The structure also reveals two conformers, termed α and β, with an αβαβαβ configuration. The existence of α and β conformers in this class of proteins was confirmed by solving the structure of DotB from another bacterial pathogen, Yersinia, where, intriguingly, we observed an ααβααβ configuration. The two conformers co-exist regardless of the nucleotide-bound states of the proteins. Our investigation therefore reveals that these ATPases can adopt a wider range of conformational states than was known before, shedding new light on the extraordinary spectrum of conformations these ATPases can access to carry out their function. Overall, the structure of DotB provides a template for further rational drug design to develop more specific antibiotics to tackle Legionnaire's disease. PDB Code(s): Will; be; provided.

Keywords: ATPase; DotB; Legionella pneumophila; Type IV secretion system; crystal structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / genetics*
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics*
  • Binding Sites
  • Crystallography, X-Ray
  • Humans
  • Legionella pneumophila / chemistry
  • Legionella pneumophila / enzymology
  • Legionella pneumophila / genetics
  • Legionnaires' Disease / microbiology
  • Mutation / genetics
  • Protein Conformation
  • Type IV Secretion Systems / chemistry*
  • Yersinia / enzymology


  • Bacterial Proteins
  • Type IV Secretion Systems
  • Adenosine Triphosphatases
  • DotB protein, Legionella pneumophila