Size and conformation limits to secretion of disulfide-bonded loops in autotransporter proteins

Denisse L Leyton, Yanina R Sevastsyanovich, Douglas F Browning, Amanda E Rossiter, Timothy J Wells, Rebecca E Fitzpatrick, Michael Overduin, Adam F Cunningham, Ian R Henderson

Research output: Contribution to journalArticlepeer-review


Autotransporters are a superfamily of virulence factors typified by a channel-forming C terminus that facilitates translocation of the functional N-terminal passenger domain across the outer membrane of Gram-negative bacteria. This final step in the secretion of autotransporters requires a translocation-competent conformation for the passenger domain that differs markedly from the structure of the fully folded secreted protein. The nature of the translocation-competent conformation remains controversial, in particular whether the passenger domain can adopt secondary structural motifs, such as disulfide-bonded segments, while maintaining a secretion-competent state. Here, we used the endogenous and closely spaced cysteine residues of the plasmid-encoded toxin (Pet) from enteroaggregative Escherichia coli to investigate the effect of disulfide bond-induced folding on translocation of an autotransporter passenger domain. We reveal that rigid structural elements within disulfide-bonded segments are resistant to autotransporter-mediated secretion. We define the size limit of disulfide-bonded segments tolerated by the autotransporter system demonstrating that, when present, cysteine pairs are intrinsically closely spaced to prevent congestion of the translocator pore by large disulfide-bonded regions. These latter data strongly support the hairpin mode of autotransporter biogenesis.

Original languageEnglish
Pages (from-to)42283-42291
Number of pages9
JournalJournal of Biological Chemistry
Issue number49
Publication statusPublished - 9 Dec 2011


  • Amino Acid Sequence
  • Bacterial Toxins/chemistry
  • Biological Transport
  • Circular Dichroism
  • Cysteine/chemistry
  • Disulfides/chemistry
  • Escherichia coli/metabolism
  • Escherichia coli Proteins/chemistry
  • Microscopy, Fluorescence/methods
  • Models, Molecular
  • Molecular Conformation
  • Molecular Sequence Data
  • Mutation
  • Plasmids/metabolism
  • Protein Conformation
  • Protein Folding
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid


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