Type II secretion systems (T2SS) translocate virulence factors from the periplasmic space of many pathogenic bacteria into the extracellular environment. The T2SS of Vibrio cholerae and related species is called the extracellular protein secretion (Eps) system that consists of a core of multiple copies of 11 different proteins. The pseudopilins, EpsG, EpsH, EpsI, EpsJ and EpsK, are five T2SS proteins that are thought to assemble into a pseudopilus, which is assumed to interact with the outer membrane pore, and may actively participate in the export of proteins. We report here biochemical evidence that the minor pseudopilins EpsI and EpsJ from Vibrio species interact directly with one another. Moreover, the 2.3 Å resolution crystal structure of a complex of EspI and EpsJ from Vibrio vulnificus represents the first atomic resolution structure of a complex of two different pseudopilin components from the T2SS. Both EpsI and EpsJ appear to be structural extremes within the family of type 4a pilin structures solved to date, with EpsI having the smallest, and EpsJ the largest, "variable pilin segment" seen thus far. A high degree of sequence conservation in the EpsI:EpsJ interface indicates that this heterodimer occurs in the T2SS of a large number of bacteria. The arrangement of EpsI and EpsJ in the heterodimer would correspond to a right-handed helical character of proteins assembled into a pseudopilus.
|Number of pages||16|
|Journal||Journal of Molecular Biology|
|State||Published - Jan 11 2008|
Bibliographical noteFunding Information:
We acknowledge Stewart Turley for help with data collection, Brian Krumm for helpful discussions about crystallization, Francis Athappilly for maintenance of our computing network and Dr Mark Strom for providing genomic DNA of V . vulnificus . We thank the staff of beamline 8.2.1 at the ALS, Berkeley for support during data collection. This research was supported by NIH grant AI34501 to W.G.J.H. from the National Institute of Allergy and Infectious Diseases (NIAID), and by the Howard Hughes Medical Institute (HHMI).
- general secretion pathway
- type 4 pilin biogenesis
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology