PSPA analysis showing representatives of the four major STE20 specificity groups.

(A) Quantified PSPA spot intensities were normalized to an average value of 1 at each position within the peptide. Log2 transformed data are depicted as heat maps showing positively and negatively selected residues by position. Data are the mean of at least two separate experiments. Numerical values are provided in S1 Data. (B) Top: Positively selected residues from PSPA analysis for the same kinases as in panel A are shown as sequence logos. Bottom: Sequence logos based on alignments of all known phosphorylation sites mapped on protein substrates for the indicated kinase. Substrate phosphorylation sites were collected from the PhosphoSitePlus database, with the exception of TAO2 substrate sites that were identified in [43]. Logos were generated with enoLOGOS [44]. MST, Mammalian sterile 20 kinase; OSR1, Oxidative stress-responsive 1; PAK, p21-activated kinase; PSPA, positional scanning peptide array; TAO2, thousand and one amino acid kinase 2