Mechanism of CDK activation revealed by the structure of a cyclinA-CDK2 complex

Abstract

The crystal structure of the human cyclinA-cyclin-dependent kinase2 (CDK2)-ATP complex has been determined at 2.3 A resolution. CyclinA binds to one side of CDK2's catalytic cleft, inducing large conformational changes in its PSTAIRE helix and T-loop. These changes activate the kinase by realigning active site residues and relieving the steric blockade at the entrance of the catalytic cleft.

Control of E2F activity by p21Waf1/Cip1

“…Two of the p21 mutants, namely p21 21,24 and p21 D53 ± 58 , possess altered protein sequence in the cyclinbox and cdk subunit binding domain respectively and are known to be unable to inhibit cdk activity (Nakanishi et al, 1995;Lin et al, 1996). Another p21 mutant, p21 D76 ± 79 , carries a mutation in the C-terminal region of the Nterminal domain that, based on the structural analysis of the closely related cdki p27 bound to a cyclin/cdk complex, would a ect a region of p21 that ®ts into the catalytic domain of the cdk partner (Je rey et al, 1995).…”

“…Structurally, the region of p21 around residue 53 to 58 within the cyclin/cdk complex lies close to the catalytic cleft of the cdk subunit (Je rey et al, 1995), suggesting perhaps that the mechanism through which p21 regulates transcription when localized to a promoter context involves modulating the activity of a catalytic subunit. However, as p21 21,24 retains the ability to regulate transcription as a Gal4 hybrid, and it is this mutated region of p21 that in the wild-type protein is likely to ®t into the cyclin box (Je rey et al, 1995), it is unlikely that a classical cyclin molecule is a critical target in the process. However, this analysis of p21 mutant derivatives does not rule out the possibility that a molecule with related structural motifs to the cyclin box is involved in mediating the observed e ects.…”

Evidence that downregulation of the M-CSF receptor is not dependent upon receptor kinase activity

“…The wide ranging inhibitory e ect of this mutation upon kinase activity indicates a structural e ect. In support of this, crystallographic data shows that the invariant Lys residue of kinases interacts with both ATP and with the invariant Asp residue at the beginning of the activating loop (D184 of cAPK, Figure 1a) when the kinase is inactive and with the invariant Glu residue of the C helix (E91 of cAPK) upon kinase activation (Je rey et al, 1995). Consequently, mutation of the invariant Lys residue would be expected to have structural consequences.…”

Characterisation of human cdc2 lysine 33 mutations expressed in the fission yeast Schizosaccharomyces pombe

“…Residues E38, E40, E41 and E42, play essential roles in the specificity of cdk and cyclin interactions (our unpublished results). Assuming that the conformational changes in cdc2 upon cyclin B binding are essentially similar to those observed in cdk2 in the cdk2-cyclin A complex [11], molecular modelling suggests that the K33R mutation may, through the R33-E51 salt-bridge, lock the cdc2 molecule in a conformation where the association with cdcl3/cyclin B is favored. This appealing hypothesis is in good agreement with the immunoprecipitation experiments where it was found that the amount of K33R-hscdc2 mutant associated with cdcl3/cyclinB was most abundant.…”

“…Lysine 33 is a nearly invariant amino acid across all the protein kinase family [20] and is involved in ATP binding by anchoring its ~-and fl-phosphate groups. The structure of the cyclinAbound cdk2 complex [11] revealed a significant translation and rotation of the cdk2 PSTAIRE helix (helix ~1, residues 44 55) when compared to free cdk2 [10], leading to the formation of the K33-R51 interaction. This movement is accompanied by a conformational change of the preceding loop (residues 38~,2) which bears residues implicated in cyclin A binding to cdc2.…”