Figure 1. The schematic diagram of threonine phosphorylation.

Enzyme-catalyzed proton transfer from the nucleophilic () group on threonine attacks the γ-phosphate () group on ATP, resulting in transfer of the phosphate group to threonine to form phosphothreonine and ADP, while this transfer is facilitated by magnesium (Mg²⁺) and threonine kinase. () indicates the enzyme base that initiates proton transfer.