Sox-containing kinase activity sensors

Figure 1.4 Sox-containing kinase activity sensors, (a) Schematic of Sox-based peptide sensors of kinase activity and (b) p-turn-focused kinase sensors inciuding C-terminai recognition eiements.

I ) Real-Time and Continuous Sensors of protein Kinase Activity Table 1.1 C-Sox-containing kinase activity sensors. 

A class of zinc ion (Zn2+) sensors, which utilized an unnatural amino acid that included the chelation-sensitive fluorophore, 8-hydroxy-4-(Af,Af-dimethylsulfonamido)-2-methylquinoline (sulfonamido oxine (Sox), Figure 1.3a), provided inspiration for a second class of kinase activity sensors [12-14]. The Sox amino acid was prepared via asymmetric synthesis and converted to the fluorenylmethyloxycarbonyl (Fmoc)-protected derivative and incorporated via SPPS into a peptide containing a proline-mediated fi-turn sequence [13]. The fl-turn was flanked by both Zn-chelating amino acids and the Sox fluorophore (Figure 1.3b). In this case, the fi-turn was included to provide preorganization... 

An essential feature of Sox-containing sensors is the differential binding affinity for Mg " " between the substrate and product (phosphorylated) peptides. A 10-to 25-fold enhancement of binding affinity for Mg " " (as measured by dissociation constant, /Cp) is observed upon phosphorylation. Therefore, substrate peptides manifest low background fluorescence, while phosphorylation results in robust fluorescence increases (three- to eightfold) in the presence of Mg " ". In the presence of Mg and ATP, these sensors accurately report kinase activity, while providing kinetic detail. The kinetic parameters (/C, and sensors are... 

---