Structural Insights into Cdk5 activation by a neuronal Cdk5 activator.

Abstract Although Cdk5 shows high sequence identity to Cdk1 and Cdk2, it can be fully activated by its neuronal activators p35/p25 nck5a and p39 nck5ai in a phosphorylation-independent manner. To understand structural basis of the Cdk5/p25 nck5a activation, the complex is modelled to assume either an obstructed or an opened conformation based on X-ray structures of the unphosphorylated or the phosphorylated Cdk2/cyclin A complex, respectively. Comparison and analysis of the two models, along with mutagenesis studies of p25 nck5a , suggest that the opened form represents more closely the structure of active Cdk5/p25 nck5a . The results provide a rationale basis for understanding the phosphorylation-independent activation of Cdk5/p25 nck5a .