The Intimin periplasmic domain mediates dimerisation and binding to peptidoglycan

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Intimin and Invasin are key virulence factors in enteropathogenic Escherichia coli and Yersinia spp.
• These proteins are classified as inverse autotransporters (Type Ve).
• They possess extracellular, transmembrane, and N-terminal periplasmic domains.

Purpose of the Study:

• To investigate the function of the periplasmic domain of Intimin, particularly its interaction with peptidoglycan.
• To characterize the structural features of the Intimin Lysin motif (LysM) domain.
• To determine if peptidoglycan binding and dimerization are general features of LysM-containing inverse autotransporters.

Main Methods:

• In vitro and in vivo binding assays to assess peptidoglycan interaction.
• Determination of dissociation constants for protein-ligand interactions.
• Solution structure determination of the Intimin LysM domain using NMR spectroscopy.
• Dimerization assays.

Main Results:

• The Intimin periplasmic domain binds peptidoglycan in vitro and in vivo, specifically under acidic conditions (Kd = 0.8 μM).
• The Invasin periplasmic domain, lacking LysM, showed weak binding.
• The Intimin LysM domain possesses a unique α-helix.
• The Intimin periplasmic domain mediates dimerization, a feature shared by other LysM-containing inverse autotransporters.

Conclusions:

• The periplasmic domain of Intimin, via its LysM motif, binds peptidoglycan under acidic conditions.
• Dimerization is a general characteristic of LysM-containing inverse autotransporters.
• Peptidoglycan binding may enhance bacterial survival in the gastrointestinal tract by providing resistance to stress.