Figure 1.

Schematic illustration of protein self-replicator. (A) An illustration for the model of Scott et al. (19) is shown. The proteome is partitioned into Q (housekeeping and growth rate-independent proteins), R (ribosome-affiliated proteins) and P (proteins belonging to neither Q nor R). R-class proteins are partly used for synthesizing themselves and partly for other proteins. The green line denotes the resource flows from nutrients to AAs by P. Yellow lines indicate proteins that are synthesized by R and allocated to R, P, and Q with fractions ϕ_R, ϕ_P, and ϕ_Q. (B) An illustration of our model is shown. The proteome is partitioned into Q, R, P₁ (P-class proteins required by AA supply), P₂ (chaperones and other proteins catalyzing protein maturation), and P₃ (proteases and other proteins promoting protein degradation). P₂-class proteins are partly used for maturating themselves and partly for others. Green lines indicate AA supply (from P₁ to R), polypeptide translation (from R to P₂), aberrant protein formation (from P₂ to P₃ or protein aggregation), and aberrant protein degradation into AAs (from P₃ to R), respectively. Yellow lines denote proteins that are matured by P₂ and allocated to Q, R, P₁, P₂, and P₃ with fractions ϕ_Q, ϕ_R, ϕ_P1, ϕ_P2, and ϕ_P3. ϕ_X (∈ {Q, R, P, P₁, P₂, P₃}) denotes the fraction of total native proteins devoted to X-class proteins.