Structure-based classification of bacterial chitooligosaccharide-specific outer membrane porins (ChiPs)
Rawiporn Amornloetwattana1, Piyakamon Bunkum1, H Sasimali M Soysa2
1School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology, (VISTEC), Wangchan Valley 555 Moo 1 Payupnai, Rayong 21210, Thailand.
The Journal of Biological Chemistry
|August 12, 2026
Summary
Chitoporins (ChiPs) in bacteria vary in structure and function. Monomeric ChiPs in E. coli and S. marcescens differ from trimeric ChiPs in marine Vibrio species, reflecting adaptations to different environments.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Chitoporins (ChiPs) are outer membrane porins specific to chitooligosaccharides.
- They are essential for marine bacteria utilizing chitin as a nutrient source.
Purpose of the Study:
- To investigate the structural and functional differences between atypical monomeric ChiPs (EcChiP, SmChiP) and typical trimeric ChiPs (VhChiP).
- To understand the evolutionary and environmental adaptations of bacterial ChiPs.
Main Methods:
- X-ray crystallography to determine the 3D structures of EcChiP and SmChiP.
- Electrophysiology to assess substrate interactions and pore properties.
- Structure-based phylogenetic analysis of bacterial ChiPs.
Main Results:
- EcChiP and SmChiP are monomeric 18-stranded β-barrels with shorter L3 loops.
- These monomeric ChiPs exhibit weaker and less selective substrate interactions compared to trimeric Vibrio ChiPs.
- Phylogenetic analysis revealed three distinct clades of bacterial ChiPs based on oligomerization and structural features.
Conclusions:
- Architectural variations in bacterial ChiPs, such as monomeric vs. trimeric structures and L3 loop length, are likely driven by environmental selection.
- Monomeric ChiPs in E. coli and S. marcescens may be adapted for variable substrate availability, contrasting with trimeric ChiPs in marine Vibrio species for efficient chitin uptake.
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