Abstract
The type III secretion system (T3SS) ATPase is the conserved and essential inner-membrane component involved in the initial stages of selective secretion of specialized T3SS virulence effector proteins from the bacterial cytoplasm through to the infected host cell, a process crucial to subsequent pathogenicity. Here we present the 1.8-Å-resolution crystal structure of the catalytic domain of the prototypical T3SS ATPase EscN from enteropathogenic Escherichia coli (EPEC). Along with in vitro and in vivo mutational analysis, our data show that the T3SS ATPases share similarity with the F1 ATPases but have important structural and sequence differences that dictate their unique secretory role. We also show that T3SS ATPase activity is dependent on EscN oligomerization and describe the molecular features and possible functional implications of a hexameric ring model.
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Acknowledgements
We thank A.L. Lovering, C.K. Yip and P.I. Lario for discussions, C.K. Yip for performing the static light-scattering analysis, N.A. Thomas for reagents and the staff at Advanced Light Source beamline 8.2.2 for data collection time and assistance. R.Z. is supported by postdoctoral fellowships from Izaak Walton Killam Research, the Michael Smith Foundation for Health Research (MSFHR) and the Canadian Institutes of Health Research (CIHR). N.C.J.S. and B.B.F. thank the Howard Hughes International Scholar program and the CIHR for funding. N.C.J.S. also thanks the MSFHR and the Canada Foundation for Innovation for infrastructure funding support. N.C.J.S. is an MSFHR Senior Scholar and CIHR Investigator.
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Supplementary information
Supplementary Fig. 1
EscN structure. (PDF 1305 kb)
Supplementary Fig. 2
Multiple sequence alignment. (PDF 1766 kb)
Supplementary Table 1
Structural comparison table. (PDF 2042 kb)
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Zarivach, R., Vuckovic, M., Deng, W. et al. Structural analysis of a prototypical ATPase from the type III secretion system. Nat Struct Mol Biol 14, 131–137 (2007). https://doi.org/10.1038/nsmb1196
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DOI: https://doi.org/10.1038/nsmb1196
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