https://pages.htgaa.org/2026a/dan-wright/homework/week-11-hw-building-genomes/index.htmlComponent‑by‑Component Breakdown Component Role in the Reaction E. coli Lysate – BL21 (DE3) Star Lysate (includes T7 RNA Polymerase) Provides the cellular machinery (ribosomes, tRNA, enzymes, T7 RNAP) for transcription and translation. The rne131 mutation enhances mRNA stability. Potassium Glutamate Optimizes ionic strength and mimics the intracellular environment, improving protein yields compared to chloride salts. HEPES-KOH pH 7.5 Maintains stable pH without precipitating metal ions like Mg²⁺, essential for ribosome function and enzyme activity. Magnesium Glutamate Mg²⁺ is a cofactor for ribosome assembly, NTP binding, and many enzymes. Glutamate counterion supports native‑like conditions. Potassium phosphate monobasic + dibasic Secondary buffering system; provides inorganic phosphate for energy regeneration (e.g., from PEP to pyruvate). Ribose Carbon source for slow energy production via metabolism, sustaining long‑term (20 h) protein synthesis. Glucose Central energy source; metabolized through glycolysis to generate ATP and NTPs over extended incubation. AMP, CMP, GMP, UMP Monophosphate nucleotides – precursors for RNA synthesis. The system phosphorylates them to NTPs using endogenous energy. Guanine Nucleobase precursor for guanine nucleotides via salvage pathways (HGPRT enzyme). Allows transcription even when GMP is omitted. 17 Amino Acid Mix, Tyrosine, Cysteine Building blocks for the target protein. Tyrosine and cysteine added separately to avoid precipitation. Nicotinamide Backfill Precursor to NAD⁺, a critical cofactor for glycolysis and energy regeneration. Nuclease Free Water Solvent; prevents degradation of DNA template and RNA by contaminating nucleases. ⚡ 1‑Hour Optimized (PEP‑NTP) vs. 20‑Hour (NMP‑Ribose‑Glucose) Master Mixes Feature 1‑Hour Optimized Mix 20‑Hour Mix Nucleotide source Pre‑assembled NTPs (ATP, GTP, CTP, UTP) NMPs + guanine (phosphorylated over time) Energy source PEP (phosphoenolpyruvate) – rapid, direct Ribose + glucose – metabolized slowly Kinetics Fast burst of high‑yield synthesis Sustained production over many hours Best for Quick protein expression (e.g., screening) Long‑term, high‑titer expression 💡 Bonus: How can transcription occur if GMP is not included but guanine is? Transcription requires GTP. The cell‑free lysate contains the guanine salvage pathway:Hugoen