(A) A histogram showing the distribution of enrichment scores for 2587 peptides upon phosphorylation by c-Abl. ‘High-efficiency’ c-Abl substrates are defined as those with enrichment scores above the dashed line in the graph. (B) Phospho-pLogo diagram showing the probability at each position of the amino acids in the high-efficiency c-Abl substrates (791 peptides) relative to all substrates in the library (2587 peptides). (C) Histogram of enrichment score distribution, as in (A), for ZAP-70. (D) Phospho-pLogo diagram, as in (B), for ZAP-70 (604 high-efficiency peptides). (E) Phospho-pLogo diagram, as in (B), for c-Src (791 high-efficiency peptides). (F) Phospho-pLogo diagram, as in (B), for Lck (763 high-efficiency peptides). Sequence logos were visualized using pLogo (O'Shea et al., 2013). In each case, the same cutoff of an enrichment score greater than or equal to 1.5 was used. Data for c-Src are the average of three independent screens, and data for c-Abl, Lck, and ZAP-70 are the average of two independent screens.