Abstract
Biosynthetic capacity, particularly in protein production, significantly influences cells' physiological efficiency and their ability to proliferate. Numerous studies have suggested that reducing protein synthesis can extend lifespan and improve indicators of cellular efficiency. However, the precise mechanism behind this phenomenon remains unclear. This study employed a model combining two methods to reduce biosynthetic activity-the deletion of genes encoding ribosomal proteins (e.g., RPL20A, RPL20B, and RPS6B) and calorie restriction-to analyse the relationships among biosynthetic capacity, cell size, and physiological efficiency. The results indicate that, under calorie restriction, parameters such as growth rate, cell size, protein content, metabolic activity, and glucose utilisation decrease significantly only in the wild-type strain. Conversely, yeast strains with deleted ribosomal protein genes-particularly Δrpl20a, which has the lowest biosynthetic capacity-exhibit a marked reduction in biosynthetic capacity under optimal conditions and no additional limiting effect from calorie restriction. These findings suggest the existence of a minimal threshold of biosynthetic capacity required to maintain a cell's physiological efficiency. Thus, factors that reduce biosynthetic efficiency only have a noticeable effect on cells with biosynthetic activity levels above the minimal threshold.