“…The major serine phosphorylation motifs were P×SP, RR×S, R××SP, SP×××R, SPP, RS×S, SP, R××S, R×S, GS, S×××××K, K××S, S××K, and S××E, while the threonine phosphorylation motif was TP, where × is any residue ( Figure 2C ). The above motifs were also observed in a phosphoproteomic analysis of broiler chicken proteins ( 34 ), suggesting that, as expected, phosphorylation modification sites are conserved across animals. A heatmap analysis of the preferences for each of these 15 amino acid sequence motifs revealed that arginine was the preferred amino acid upstream of the phosphorylated serine or threonine residue ( Figures 2D, E ), while proline was preferred to be located downstream ( Figures 2D, E ).…”