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Team:KULeuven/Project/Memory
From 2008.igem.org
Contents |
Memory
BioBricks
Components
[http://partsregistry.org/Part:BBa_C0052 BBa_C0052] is the cI repressor from phage 434, modified with an LVA-tag. It is placed under control of [http://partsregistry.org/Part:BBa_R0053 BBa_R0053], the phage P22 cII regulated promoter. [http://partsregistry.org/Part:BBa_C0053 BBa_C0053] codes for this cII P22 repressor protein and is placed under control of a standardised right cI 434 promoter [http://partsregistry.org/Part:BBa_R1052 BBa_R1052]. A third subdivision consists of the [http://partsregistry.org/Part:BBa_C0052 BBa_C0052] cI repressor from phage 434 under control of the TetR promoter [http://partsregistry.org/Part:BBa_R0040 BBa_R0040]. In this instance however, the cI 434 protein is not LVA-tagged. The fourth and last subdivision is an antisense LuxI mRNA (encoded by [http://partsregistry.org/Part:BBa_K145013 BBa_K145013]) once again under control of the standardised right cI 434 promoter [http://partsregistry.org/Part:BBa_R1052 BBa_R1052].
Action
Now for how this memory device works. When there is no signal from the input device (through [http://partsregistry.org/Part:BBa_R0040 the TetR promoter]), and there has never been one, the P22 c2 repressor will gain control over the system. P22 c2 and not 434 cI controls this OFF state because it has a lower Kd, a stronger promoter ([http://partsregistry.org/Part:BBa_R1052 BBa_R1052] vs [http://partsregistry.org/Part:BBa_R0053 BBa_R0053]) for its transcription and a more efficient RBS for its translation ([http://partsregistry.org/Part:BBa_B0031 BBa_B0031] vs [http://partsregistry.org/Part:BBa_B0033 BBa_B0033]) than cI 434. This means that the synthesis of [http://partsregistry.org/Part:BBa_C0052 cI 434 (LVA)] mRNA will be rapidly and strongly repressed from the [http://partsregistry.org/Part:BBa_R0053 c2 P22 promoter]. In the mean time, transcription can proceed from the [http://partsregistry.org/Part:BBa_R1052 cI 434 promoter], thus continuing c2 P22 synthesis as well as antisense LuxI RNA from the same promoter, further imposing the OFF state of the memory on the system. The antisense LuxI will disrupt LuxI translation, inhibiting an untimely timer causing untimely cell death.
When an input signal emerges, the [http://partsregistry.org/Part:BBa_C0052 long-lived 434 cI] repressor is made from the input [http://partsregistry.org/Part:BBa_R0040 TetR promoter]. The produced cI 434 will repress transcription of [http://partsregistry.org/Part:BBa_C0053 P22 c2 repressor] through the [http://partsregistry.org/Part:BBa_R1052 cI 434 promoter].
This turns the phage 22 promoter on, resulting in further production of phage 434 cI repressor. Antisense LuxI production ceases, and LuxI begins producing HSL.
From now on, phage 434 cI repressor accumulates and phage 22 cII inhibitor concentrations quickly drop to zero. This is nicely pictured on the modeling page of the memory system.
Input
Output
Filter
InverTimer
Reset
Cell Death
Memory
