User:Cheuk Ka Tong/Sandbox2

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Pore Proteins

In light of the specification of the Cell By Date system to last for at least 24 hours, the team has looked into different ways to prolong the cell-free expression system. Based on A vesicle bioreactor as a step toward an artificial cell assembly by Vincent Noireaux and Albert Libchaber, transcription-translation of plasmid genes stops after 2 hours, whille encapsulaiton of cell extract into phospholipid vesicles surrounded by feeding solution prolongs the expression system by up to 5 hours. When pore proteins are expressed inside the vesicles to create selective permeability for nutrients, the system sustains expression for up to 4 days. Having separately achieved in-vitro expression and formation of vesicles, the team is now working on putting cell extract into vesicles. This page looks at the possible candidates of pore proteins we can employ to attain the desired selective permeability in the vesicles.

Specifications for pore proteins

  • Non-toxic
  • Accessible
  • Affordable
  • Compatible with lipids used (DOPC/POPC)
  • Forms a pore of ~1.4nm in diameter, or
  • Molecular mass cut-off of ~3kDa


List of pore protein candidates

No.Pore proteinDescriptionToxicityPore sizeCompatibility with lipidsAccessibility/affordability
1α-Hemolysin toxinDerived from S. aureus
Expressed as a monomer and assembles into heptamer at the membrane
Channel comprises a 14-strand beta barrel
Pore remains open at neutral pH and high ionic strength
Toxic1.4nm in diameter
Molecular mass cut-off of 3kDa
Forms pores in lipid bilayers composed of phosphatidylcholine/
phosphatidylethanolamine
2Mitochondrial porin (VDAC)Located in the mitochondrial outer membrane
Monomeric protein
Non-toxic3nm in diameter
Molecular mass cut-off of 3.4 kDa
Large enough for dsDNA to pass through
Available from Abcam
Product no. ab16131
GBP99.00 for 0.1mg
3OmpF porinLocated in the E. coli outer membrane
Homotrimeric protein
Each monomer consists of a 16-stranded beta-barrel
Non-toxic1.2nm in diameter
Large enough for ssDNA to pass through
4OmpG porinLocated in the E. coli outer membrane
Most likely functions as a monomer
Consists of 14 beta-strands
Non-toxic1.3nm in diameter
5OmpC porinLocated in the E. coli outer membraneNon-toxic
6PhoE porinLocated in the E. coli outer membraneNon-toxic
7Magainin 2Derived from African clawed frog Xenopus laevis
Peptide antibiotic with antibacterial and antiparasitic activities
Assumes an amphiphilic helix when bound to the lipid
FW = 2466.90
Non-toxic1.6nm in diameterForms pores in DOPC/DOPG lipid bilayers
Forms pores in POPC/DOPS or POPC/DOPG
Does not form pores in POPC alone
Forms pores in anionic lipids but not in zwitterionic lipids
Used in 3-10μM concentrations
Available from Sigma
Product no. M7402
GBP285.00 for 1mg
Also available from Cambridge Bioscience
Product no. ANA20640
GBP112.00 for 1mg
8Magainin 1Derived from African clawed frog Xenopus laevis
Peptide antibiotic with antibacterial and antiparasitic activities
Non-toxic Available from Sigma
Product no. M7152
GBP290.50 for 1mg
Also available from Cambridge Bioscience
Product no. ANA20792
GBP112.00 for 1mg
9Cecropin APeptide antibiotic with antibacterial and antiparasitic activitiesNon-toxic Available from Sigma
Product no. C6830
GBP83.10 for 0.1mg
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