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In order for the cross-feeding scheme to work we need each strain to export the amino acid they produce (either Histidine or Tryptophan). To achieve this we created a devices design to secrete to the medium an His (or Trp) rich peptides.

Basic DNA structure of the devices with their constitutive parts

• Kozak consensus sequence for initiation of translation.
• Signal peptide that targets the product of the gene for secretion.
• Trojan peptide to increase internalization in target cell.
• Payload: this is the exported amino acid rich domain of the protein.

The input of the devices are PoPS and the output is secreted amino acids, so the devices are PoPS -> exported AA transducers. In principle any PoPS generating part can be used.

You can read more about the design process here

We built 2 His-export devices, and 2 Trp-export devices:

• His-export I (<partinfo>BBa_K792009</partinfo>)
• Trp export I (<partinfo>BBa_K792010</partinfo>)
• His-export II (<partinfo>BBa_K792011</partinfo>)
• Trp export II (<partinfo>BBa_K792012</partinfo>)

To achive this, we had to create several new basic biobricks:

• Kozak sequence from yeast α-factor mating pheromone (MFα1) (<partinfo>BBa_K792001</partinfo>)
• Secretion tag from yeast α-factor mating pheromone (MFα1) (<partinfo>BBa_K792002</partinfo>)
• HIV TAT penetratin (<partinfo>BBa_K792003</partinfo>)
• Polyarginine trojan peptide (<partinfo>BBa_K792004</partinfo>)
• PolyHa, a Histidine rich peptide (His-Tag) (<partinfo>BBa_K792005</partinfo>)
• TrpZipper2, a Tryptophan rich peptide water soluble and monomeric (<partinfo>BBa_K792006</partinfo>)
• PolyHb, a stable Histidine rich peptide designed by us (<partinfo>BBa_K792007</partinfo>)
• PolyWb, a stable Tryptophan rich peptide designed by us(<partinfo>BBa_K792008</partinfo>)