Figure 4.

Preference for positive charge at positions located N-terminally with regard to the phosphorylated site. The upper graph depicts the increased occurrence of positively charged residues (His, Lys, Arg) compared to the expected database occurrence of 13.6% (deduced from UNIREF). The lower part of the figure shows the correlation coefficients R between amino acid frequencies and ZIMJ680104 (isoelectric point) [87] property values. Both plots demonstrate that the preference for basic residues is highest at positions -3 and -2, but encompasses at least the entire region between amino acids -6 and -2.