Effects of Asp-N-cleaved activated Rho (Asp-NRho*) on peptide C phosphorylation by GRK1535H6. Both the wt protein (■) and the cross-linked T8C/N480C mutant (□) show activation by Asp-N Rho* in a concentration-dependent fashion, while the ΔN19 mutant did not show activation by Asp-NRho* (●). Data were fitted to eq 1 from four independent experiments. Ymin, Ymax, and KD,app values are (79 ± 5) × 10−6 s−1, (780 ± 80) × 10−6 s−1, and 12 ± 5 µM for wt and (370 ± 40) × 10−6 s−1, (1900 ± 170) × 10−6 s−1, and 15 ± 6 µM for the cross-linked T8C/N480C mutant, respectively.