The mechanism of inhibition of the cyclin-dependent kinase-2 as revealed by the molecular dynamics study on the complex CDK2 with the peptide substrate HHASPRK.

Molecular dynamics (MD) simulations were used to explain structural details of cyclin-dependent kinase-2 (CDK2) inhibition by phosphorylation at T14 and/or Y15 located in the glycine-rich loop (G-loop). Ten-nanosecond-long simulations of fully active CDK2 in a complex with a short peptide (HHASPRK) substrate and of CDK2 inhibited by phosphorylation of T14 and/or Y15 were produced. The inhibitory phosphorylations at T14 and/or Y15 show namely an ATP misalignment and a G-loop shift (~5 A) causing the opening of the substrate binding box. The biological functions of the G-loop and GxGxxG motif evolutionary conservation in protein kinases are discussed. The position of the ATP gamma-phosphate relative to the phosphorylation site (S/T) of the peptide substrate in the active CDK2 is described and compared with inhibited forms of CDK2. The MD results clearly provide an explanation previously not known as to why a basic residue (R/K) is preferred at the P(2) position in phosphorylated S/T peptide substrates.