Quantitative protein interaction mapping. Quantitative data were obtained by probing SH2/PTB domain microarrays with fluorescently labeled peptides derived from Tarp. The resulting data were used to construct quantitative protein interaction maps. White circles within the square represent peptides derived from C. trachomatis. Peptide allocation can be derived from Table S1 and the peptide legend, which shows phosphorylation status and position within the full-length protein. For example, peptide 2 in A mimics the three identical ENIYE repeats of serovar D Tarp in the nonphosphorylated state. Green and blue circles around the square represent individual SH2 and PTB domains, respectively. Circles outside the square indicate tandem domains (the corresponding spot on the protein array contains both domains), which are connected to their individual domains (i.e., full-length SYK is in possession of two SH2 domains located either N or C terminally). A color-coded line is used to reflect the measured interaction strength between each domain–peptide pair (n = 2). Exact values are provided in Table S1. Interactions with K_D ≥ 2 µM are omitted. (A and B) Interaction maps of nonphosphorylated Tarp D and L2. (C and D) Interaction maps of singly phosphorylated Tarp D and L2. (E) Interaction map of doubly phosphorylated Tarp from serovariant L2.