Figure 3
From: Upstream plasticity and downstream robustness in evolution of molecular networks
Divergence of downstream functions of duplicated genes in the baker's yeast S. cerevisiae. A. The average value of the interaction overlap Ω int – the number of physical interaction partners shared by a pair of paralo-gous proteins – as a function of the similarity of their amino acid sequences. The physical interaction data are taken from the set of Uetz et al. [3] (open circles), the core dataset of Ito et al. [4] (diamonds), and the non-redundant combination of the two (filled circles). Note the apparent plateau for PID's between 70% and 100% in all three datasets. Solid lines are guides for the eye. A randomly selected (usually non-paralogous) pair of proteins in the combined dataset on average has Ω int around 8 × 10-3 (off-limits in this figure). All data points at all PIDs are significantly above this null-model value. B. The fraction of essential (lethal null-mutant) proteins among all proteins tested in Ref. [5] as a function of PID to their most similar paralog in the yeast genome. Proteins with no paralogs (singletons) are binned at 0% PID. Note the apparent plateau between 50% and 100% PID. The inset (note the change of scale on the y-axis) shows the fraction of essential proteins in the subset of all proteins known to be localized in the yeast nucleus [17]. Here the effect becomes even more pronounced so that all 18 nuclear proteins protected by a paralog with at least 50% similarity were found to be non-essential.