Figure 4. Translation machinery in S. cerevisiae optimizes for ribosomal cost, flexible regulation and production capacity.

All rates are in codons per second, while currents are measured in ribosomes per second. A: 850 genes of S. cerevisiae are located in the phase diagram, with size and hue of each data point reflecting current and minimum elongation rate, respectively. On a population level, systems of comparable production capacities (∝ λ_min) fully exploit their dynamic range by adjustment of α, with highly expressed proteins likely situated inside or close to MC. B: The resulting resource cost considerations drive a significant number of transcripts to position their minimum elongation rate early on in the codon sequence, forcing ribosomal traffic jams to remain short. C: Initiation α is the main determinant of currents, at least for low to average current genes. For highly expressed genes, the correlation between α and J decreases due to stronger variation in λ₀ and transitions into MC. D: Genes utilize the full dynamical range of currents set by λ_min, through variation in α and λ₀. Constitutively highly expressed genes tend to be closer to maximum capacity (red line), while genes with variable expression demands are distributed more broadly (see main manuscript). E: For fixed production capacity ∝ λ_min, α* (the critical initiation rate at which genes reach maximum production capacity) tends to be smaller for genes with larger production rates. That is, larger λ₀ (which are inversely related to α* for fixed λ_min) seem to facilitate attainment of large currents. Moreover, within highly expressed genes, those associated with variable expression patterns over time exhibit higher sensitivities (smaller α*), whereas genes with constitutive high expression are found closer towards maximal insensitivity (dotted red line) as these configurations ease stable expression.