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From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Porins in prokaryotes and eukaryotes: common themes and variations
1Max Planck Institute of Developmental Biology, Department Protein Evolution, Spemannstr. 35, D-72076 Tübingen, Germany. kornelius.zeth@tuebingen.mpg.de
The Biochemical Journal
|September 15, 2010
Summary
Gram-negative bacteria and mitochondria share outer membrane channels called porins, crucial for metabolite transport. Bacterial porins typically have even beta-strands, while mitochondrial VDAC channels have an odd number, despite similar structures.
Area of Science:
- Biochemistry
- Cell Biology
- Evolutionary Biology
Background:
- Gram-negative bacteria and mitochondria possess dual biological membranes, a conserved feature from early evolutionary stages.
- Outer membranes in both systems contain porin channels facilitating the transport of ions and small molecules like nucleosides and sugars.
- Bacterial porins, typically beta-barrels with an even number of beta-strands (14-18), contrast with mitochondrial VDAC channels, which possess 19 beta-strands.
Purpose of the Study:
- To review and compare the structural and functional principles of porin protein families in Gram-negative bacteria and mitochondria.
- To highlight the commonalities and differences in the assembly, architecture, and function of these essential membrane channels.
- To explore the evolutionary context of these conserved yet distinct porin structures.
Main Methods:
- Comparative structural analysis of bacterial outer membrane porins and mitochondrial VDAC.
- Review of existing literature on porin biogenesis, channel function, and evolutionary relationships.
- Analysis of beta-barrel architecture in both bacterial and mitochondrial porins.
Main Results:
- Both bacterial porins and mitochondrial VDACs share a beta-barrel architecture for metabolite transport.
- A key difference lies in the number of beta-strands: even (14-18) in bacteria versus odd (19) in VDAC.
- Despite structural similarities, a direct evolutionary link between bacterial porins and VDAC remains unclear.
Conclusions:
- Porin channels in bacteria and mitochondria, though functionally analogous, exhibit distinct structural features, particularly in beta-strand count.
- The conserved presence of porins underscores their fundamental importance in cellular transport across different life forms.
- Further research may elucidate the evolutionary pathways leading to these specialized channel proteins.
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