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A common channel-forming motif in evolutionarily distant porins
R A Pauptit1, T Schirmer, J N Jansonius
1Biocenter, University of Basel, Switzerland.
Journal of Structural Biology
|October 1, 1991
Summary
Four new crystal structures of Escherichia coli porins reveal a conserved 16-stranded antiparallel beta-barrel motif. This structural similarity suggests a fundamental role for beta-barrels in bacterial membrane channels across diverse species.
Area of Science:
- Structural biology
- Microbiology
- Biophysics
Background:
- Escherichia coli porins are essential outer membrane proteins involved in transport.
- Understanding porin structure is crucial for deciphering bacterial outer membrane function.
Purpose of the Study:
- To determine the crystal structures of four new Escherichia coli porins.
- To investigate the structural conservation of porins across different bacterial species.
Main Methods:
- Molecular replacement methods were employed using a polyalanine trial model.
- X-ray diffraction data were analyzed to determine structural parameters.
Main Results:
- Four new crystal packings of Escherichia coli porins (phosphoporin, maltoporin, and two matrix porin forms) were determined.
- A conserved 16-stranded antiparallel beta-barrel motif was identified, similar to that in Rhodobacter capsulatus porin.
- A consistent tilt of beta-strands (30-40 degrees) relative to the membrane normal was observed across all studied porins.
Conclusions:
- The 16-stranded antiparallel beta-barrel is a conserved structural motif in bacterial porins, even with low sequence homology.
- This conserved structure suggests a fundamental role in bacterial membrane channel formation.
- The findings highlight the evolutionary significance of the beta-barrel structure in bacterial outer membranes.