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Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly
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LptA assembles into rod-like oligomers involving disorder-to-order transitions

Carlo Santambrogio1, Paola Sperandeo, Riccardo Villa

  • 1Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126, Milan, Italy.

Journal of the American Society for Mass Spectrometry
|July 31, 2013
PubMed

Insights

Lipopolysaccharide transport protein A (LptA) forms oligomers, creating a bridge for LPS transport in bacteria. Oligomerization enhances LptA stability and influences its structure, crucial for bacterial cell envelope function.

Area of Science:

  • Bacterial cell envelope biogenesis
  • Protein structure and dynamics
  • Membrane protein transport

Background:

  • LptA facilitates lipopolysaccharide (LPS) transport from the inner membrane (IM) to the outer membrane (OM) in Gram-negative bacteria.
  • LptA is proposed to oligomerize, forming a bridge between the bacterial membranes for LPS translocation.

Purpose of the Study:

  • To investigate the assembly process and structural architecture of LptA oligomers.
  • To understand how LptA oligomerization affects its conformational stability and function.

Main Methods:

  • Circular dichroism (CD) spectroscopy to analyze protein structure.
  • "Native" electrospray-ionization ion-mobility mass spectrometry (ESI-IM-MS) to study oligomer morphology and stoichiometry.
  • Thermal denaturation assays to assess protein stability.

Main Results:

  • LptA progressively assembles into concentration-dependent, rod-like oligomers with no fixed stoichiometry, growing via an n+1 mechanism up to at least the pentamer.
  • Oligomerization induces disorder-to-order transitions in LptA, involving N- and C-terminal regions, and significantly increases protein stability against thermal denaturation.
  • LPS binding further enhances LptA conformational stability.

Conclusions:

  • LptA oligomerization is a key feature for its function in LPS transport, involving structural rearrangements and enhanced stability.
  • The formation of fibrillar LptA structures is critical for efficient LPS translocation across the bacterial periplasm.
  • Understanding LptA assembly provides insights into bacterial cell envelope maintenance and potential therapeutic targets.

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