Figure 2. Phosphates at different sites vary widely in their tendency to stimulate or inhibit arrestin activation and binding.
Typical contributions of phosphate addition at each site to activation (A) and binding strength (D). A positive value indicates that phosphate addition at a given site typically promotes activation/binding, and a negative value indicates that phosphate addition typically inhibits activation/binding, but the effect of phosphorylating a particular site can vary substantially depending on which other sites are phosphorylated. B Adding phosphate pS357 to a peptide phosphorylated at T360 substantially reduces arrestin activation; C K294 of arrestin’s gate loop moves away from pT360 to engage pS357, hindering the interdomain twisting motion associated with activation. E Adding pS362 to a peptide phosphorylated at S350 substantially reduces binding; F K294 swings down to engage pS362, causing rearrangement of a polar network near the tail-binding interface and thus disrupting interactions between the arrestin N terminus and the V2R C-tail. Whiskers in box plots represent the 5th and 95th percentiles of the distributions for each simulation condition. See also Figure S1–S3.