Borrelia burgdorferi lipoproteins are secreted to the outer surface by default

Mol Microbiol. 2006 Mar;59(5):1473-84. doi: 10.1111/j.1365-2958.2006.05039.x.

Abstract

Borrelia spirochaetes are unique among diderm bacteria in their abundance of surface-displayed lipoproteins, some of which play important roles in the pathogenesis of Lyme disease and relapsing fever. To identify the lipoprotein-sorting signals in Borrelia burgdorferi, we generated chimeras between the outer surface lipoprotein OspA, the periplasmic oligopeptide-binding lipoprotein OppAIV and mRFP1, a monomeric red fluorescent reporter protein. Localization of OspA and OppAIV point mutants showed that Borrelia lipoproteins do not follow the '+2' sorting rule which targets lipoproteins to the cytoplasmic or outer membrane of Gram-negative bacteria via the Lol pathway. Fusions of mRFP1 to short N-terminal lipopeptides of OspA, and surprisingly OppAIV, were targeted to the spirochaetal surface. Mutagenesis of the OspA N-terminus defined less than five N-terminal amino acids as the minimal secretion-facilitating signal. With the exception of negative charges, which can act as partial subsurface retention signals in certain peptide contexts, lipoprotein secretion occurs independent of N-terminal sequence. Together, these data indicate that Borrelia lipoproteins are targeted to the bacterial surface by default, but can be retained in the periplasm by sequence-specific signals.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antigens, Surface / genetics
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bacterial Vaccines
  • Borrelia burgdorferi / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Membrane / metabolism*
  • Lipoproteins / genetics
  • Lipoproteins / metabolism*
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Molecular Sequence Data
  • Mutation
  • Protein Sorting Signals
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism

Substances

  • Antigens, Surface
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Bacterial Vaccines
  • Carrier Proteins
  • Lipoproteins
  • Luminescent Proteins
  • OspA protein
  • Protein Sorting Signals
  • Recombinant Fusion Proteins
  • oligopeptide-binding protein, bacteria
  • red fluorescent protein