Week 11 Homework: Bioproduction & Cloud Labs

Homework: Master Mix Component Analysis

Referencing the cell-free protein synthesis reaction composition, provide a 1-2 sentence description of what each component’s role is in the cell-free reaction.

1. E. coli Lysate

  • BL21 (DE3) Star Lysate: Provides the core machinery for translation (ribosomes, tRNAs) and T7 RNA Polymerase for transcription; the “Star” mutation specifically helps by reducing mRNA degradation during the reaction.

2. Salts/Buffer

  • Potassium Glutamate: Acts as the primary salt to maintain the necessary ionic strength and provides a potassium source essential for ribosomal catalytic activity.
  • HEPES-KOH pH 7.5: A robust chemical buffer used to maintain a stable pH environment as metabolic byproducts accumulate over the 20-hour run.
  • Magnesium Glutamate: Supplies magnesium ions, which are critical cofactors for ribosomal assembly and the function of various enzymes in the lysate.
  • Potassium phosphate (monobasic/dibasic): Serves as a secondary buffer system and provides the inorganic phosphate required for the regeneration of ATP.

3. Energy / Nucleotide System

  • Ribose & Glucose: These act as the primary carbon and energy sources, which the lysate’s internal metabolic pathways utilize to regenerate ATP and GTP for long-duration production.
  • AMP, CMP, GMP, UMP: These nucleoside monophosphates serve as the foundational, recyclable building blocks that the lysate converts into active NTPs for transcription.
  • Guanine: A specific nucleobase precursor that allows the salvage pathway to synthesize additional GTP when initial pools are exhausted.

4. Translation Mix (Amino Acids)

  • 17 Amino Acid Mix: Supplies the majority of the essential building blocks needed to assemble the polypeptide chain.
  • Tyrosine: Added separately due to its extremely low solubility at neutral pH, which would cause it to precipitate out of a combined master mix.
  • Cysteine: Added separately because it is highly reactive and prone to oxidation, which can lead to unwanted disulfide bond formation if not managed.

5. Additives & Backfill

  • Nicotinamide: A precursor for NAD+/NADH redox cofactors, essential for maintaining the metabolic flux of the energy regeneration system over 20+ hours.
  • Nuclease Free Water: The solvent used to bring the reaction to its final volume while ensuring no contaminating enzymes are introduced to degrade the DNA or RNA templates.

Homework: Reaction Dynamics

Describe the main differences between the 1-hour optimized PEP-NTP master mix and the 20-hour NMP-Ribose-Glucose master mix.

The 1-hour PEP-NTP mix is designed for high-speed “sprint” production, utilizing high-energy Phosphoenolpyruvate (PEP) and pre-formed NTPs for immediate reaction. In contrast, the 20-hour NMP-Ribose-Glucose mix is built for a “marathon,” using cheaper precursors (NMPs and sugars) and relying on the lysate’s endogenous metabolic salvage pathways to sustain energy and nucleotide production over a significantly longer period.

Bonus question: How can transcription occur if GMP is not included but Guanine is?

Transcription is possible because the E. coli lysate contains salvage pathway enzymes that can convert Guanine into GMP by adding a phosphoribosyl group. This GMP is then further phosphorylated by kinases within the lysate into GTP, which is the required substrate for RNA polymerase to perform transcription.

Homework: Part C — Planning the Global Experiment

Given the 6 fluorescent proteins used, identify and explain at least one biophysical or functional property of each protein that affects expression or readout in cell-free systems.

  • sfGFP: Features extremely robust folding and fast maturation, making it the most reliable reporter across various lysate conditions and temperatures.
  • mRFP1: Characterized by a relatively slow maturation time, meaning its fluorescence signal often lags significantly behind the actual translation of the protein.
  • mKO2: An exceptionally bright orange protein, but it can be sensitive to photobleaching during the repeated reads of a long 36-hour experiment.
  • mTurquoise2: Possesses an exceptionally high quantum yield (brightness), allowing for high-sensitivity detection even when total protein yields are low.
  • mScarlet_I: One of the brightest red proteins available, but it has a high oxygen requirement for chromophore maturation, which can limit signal in deep, stagnant wells.
  • Electra2: Specifically engineered for high stability and rapid maturation, providing near real-time data on the rate of protein production in cloud lab setups.

Create a hypothesis for how adjusting one or more reagents in the cell-free mastermix could improve a specific biophysical or functional property.

Target Protein: mScarlet_I
Reagent Adjustment: Increase Glucose and Nicotinamide by 25%.
Hypothesis: Because mScarlet_I has a slow, energy-intensive maturation process, increasing the primary fuel (Glucose) and its metabolic cofactors (Nicotinamide) will extend the metabolic lifespan of the reaction. This sustained energy availability will allow more protein molecules to complete their final oxygen-dependent maturation step over a 36-hour incubation, maximizing total fluorescence.

Gemini AI was consulted for data synthesis and formatting