Part:BBa_K3128017

OmpX-WT protein fused with T18 subpart of Bordetella Pertussis AC under constitutive promoter

Sequence and features

This biobrick is composed of the external membrane Outer Membrane Protein x Wild Type (OmpX-WT) protein fused at its N-terminal end with a 54 aa GGS linker BBa_K3128010 followed by the T18 subunit of the Bordetella Pertussis adenylate cyclase (AC) BBa_K1638004 .
This biobrick is under a constitutive promoter (J23101) , thereby the expression of the OmpX-WT fused with T18 protein is always activated in order to have a large amount of recombinant protein in the membrane at any time.

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal NheI site found at 7
  Illegal NheI site found at 30
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BamHI site found at 1339
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 880
  Illegal NgoMIV site found at 1290
  Illegal AgeI site found at 1096
  
• 1000
  COMPATIBLE WITH RFC[1000]

Usage and Biology

In 1989, Fields and Song demonstrated a new genetic system allowing protein-protein interaction detection ⁽¹⁾. At first, it was done in Saccharomyces cerevisiae yeast and it was called the yeast two-hybrid assay (Y2H). In 1998, Ladant and al. described the system in bacteria ⁽²⁾. Nowadays, this biological technique is mostly used to show and characterize the physical interaction between two cytosolic proteins or internal membrane proteins in vivo ⁽³⁾.

Bacterial Adenylate Cyclase Two-Hybrid (BACTH) :

The principle lies on the interaction-mediated reconstitution of a signalling cascade in Escherichia coli. The messenger molecule involved in this cascade is the cyclic adenosine monophosphate (cAMP) produced by the adenylate cyclase. Adenylate cyclase is an enzyme catalysing the cAMP production from ATP. It physiologically participates to the cellular transmission.

This system involves the Bordetella pertussis adenylate cyclase. You might know this bacterium; it is the responsible agent for the pertussis disease. It adenylates cyclase catalytic domain has the particularity to be splittable in two distinct parts: T18 and T25 sub-parts, unable to work unless they reassociate. Each sub-part of the enzyme is fused with a protein of interest, either the bait or the prey protein chose beforehand by the experimentator.

If the proteins interact, then T18 and T25 are bring together and reconstitute a functional adenylate cyclase enzyme thus enabling cAMP production. Using cya- bacteria – strain for whom the adenylate gene is deleted, involving an absence of this endogenous enzyme – a BACTH could be done with the creation of two fusion proteins : the first one, fused at its N or C terminal intracellular end with the T18 fragment; the second one fused with the T25 fragment.
The interaction of these proteins of interest will lead to the adenylate cyclase reconstitution, thus initiating cAMP production. The cAMP produced will act as a messenger by fixing itself to the transcriptional activator CAP, cAMP form the CAP-cAMP complex, controlling the expression of the promoter lactose by initiating transcription of the following gene.
This promoter is placed upstream from the chosen reporter gene.

NeuroDrop Project - Membrane BACTH

iGEM Grenoble-Alpes team have chose to create a membrane bacterial two hybrid by using the OmpX protein, fused with adenylate cyclase subparts.

As part of the iGEM Grenoble-Alpes 2019 project, the constitutive promoter allows the bacteria to have a huge quantity of proteins located at the membrane before the detection of the target in the external environment. In addition, the team needs just one gene under cAMP inducible CAP dependant plac promoter in its final system: the reporter gene, in order to do a membrane Bacterial Adenylate Cyclase Two Hybrid.

This biobrick constitutes a part of the mBACTH system that the team used as a negative control of this assay. Indeed, this biobrick with BBa_K3128018 allow to have OmpX proteins fused to the two subunits of the adenylate cyclase from Bordetella Pertussis that move freely in the membrane. This condition enables the team to estimate the number of false positive in their system.

References

⁽¹⁾ Fields S, Song O. A novel genetic system to detect protein–protein interactions. Nature [Internet]. 1989

⁽²⁾ Karimova G, Pidoux J, Ullmann A, Ladant D. A bacterial two-hybrid system based on a reconstituted signal transduction pathway. PNAS [Internet]. 1998

⁽³⁾ Karimova G, Gauliard E, Davi M, P.Ouellette S, Ladant D. Protein–Protein Interaction: Bacterial Two-Hybrid. 2017