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Structure of the translocator domain of a bacterial autotransporter
Author(s) -
Oomen Clasien J,
van Ulsen Peter,
Van Gelder Patrick,
Feijen Maya,
Tommassen Jan,
Gros Piet
Publication year - 2004
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600148
Subject(s) - bacterial outer membrane , biology , transport protein , translocator protein , biophysics , microbiology and biotechnology , biochemistry , escherichia coli , gene , neuroinflammation , immunology , inflammation
Autotransporters are virulence‐related proteins of Gram‐negative bacteria that are secreted via an outer‐membrane‐based C‐terminal extension, the translocator domain. This domain supposedly is sufficient for the transport of the N‐terminal passenger domain across the outer membrane. We present here the crystal structure of the in vitro ‐folded translocator domain of the autotransporter NalP from Neisseria meningitidis , which reveals a 12‐stranded β‐barrel with a hydrophilic pore of 10 × 12.5 Å that is filled by an N‐terminal α‐helix. The domain has pore activity in vivo and in vitro . Our data are consistent with the model of passenger‐domain transport through the hydrophilic channel within the β‐barrel, and inconsistent with a model for transport through a central channel formed by an oligomer of translocator domains. However, the dimensions of the pore imply translocation of the secreted domain in an unfolded form. An alternative model, possibly covering the transport of folded domains, is that passenger‐domain transport involves the Omp85 complex, the machinery required for membrane insertion of outer‐membrane proteins, on which autotransporters are dependent.