Table 1. Properties of phosphorylation sites on protein binding interfaces.

“Abundance” row shows p-value of Fisher exact test of association between being phosphorylated and location on binding interface (compared to surface). Other rows present p-values calculated by Wilcoxon rank-sum test showing the difference between phosphosites and non-phosphosites on binding interfaces with respect to different properties. Significant p-values (after Holm-Bonferroni correction) showing enrichment of phosphosites with a given property are shown with asterisks. “Protomer ASA” is accessible surface area of a given protomer without binding partner; “ΔASA” is the difference in accessible surface area upon complex formation, “Hydrogen bonds” is the number of hydrogen bonds per site, “Residue contacts” is the number of residue-residue contacts per site, “Conservation” is evolutionary conservation of site. “ΔΔG^ala” is the difference in binding energy upon Ala substitution and “ΔΔG^p” is the difference in binding energy upon attaching phosphate groups to phosphorylated sites on interfaces. Note that the p-values for ΔΔG^p indicate whether the distribution is significantly shifted to positive values. See also Figure S1 and S2.

	All	All	All	Homooligomers
		Hetero	Homo	Weak	Strong	Permanent
Abundance on Interface	*1.5e-13	*7.4e-15	0.097	*8.2e-04	0.417	0.054
Structural properties
Protomer ASA	*2.2e-16	*2.2e-16	0.065	0.057	0.318	0.137
ΔASA	*4.5e-08	*1.7e-09	0.482	0.609	0.361	0.050
Hydrogen bonds	*5.9e-05	*5.3e-04	*0.043	*0.042	0.272	0.202
Residue contacts	*2.8e-04	*1.1e-03	0.217	0.502	0.424	0.452
Energetic properties
ΔΔGala	*1.8e-03	*2.7e-04	0.494	0.181	0.670	0.390
ΔΔGp	*2.2e-16	*1.3e-12	*1.3e-08	*2.8e-05	*1.1e-04	*1.6e-05
Evolutionary conservation	*0.018	*0.016	0.296	0.558	0.113	0.654