Figure 4: Normalized 3D PTM occurrence. Number of PTM pairs on Y-axis, distance between pairs in percentile protein size on X-axis. A) Distances between PTMs in our experimental datsaset. When corrected for outliers created by large proteins and adjusted to removed sites already close in sequence, a peak in inter-PTM distance was observed that was significantly lower than would be expected by chance. Median value in red, at 27th percentile; B) Equivalent normalized distribution for random PTMs within an idealised cuboid ‘protein’. Median value in black, at 37th percentile.