Summary
Arginine residues have a greater propensity to form protein-protein interactions than lysine residues (1). As a result RK substitutions in surface-exposed residues are not as common as DE substitutions.
1.
Levy ED, De S, Teichmann SA. Cellular crowding imposes global constraints on the chemistry and evolution of proteomes. Proceedings of the National Academy of Sciences. 2012;109(50):20461–6. Available from: https://doi.org/10.1073/pnas.1209312109