Cyclin Dependent Kinase 5 Regulatory Subunit 2 (CDK5R2)

Cyclin-dependent kinase 5 activator 2 is a neuron-specific activator of CDK5 kinase. It associates with CDK5 to form an active kinase. This protein and neuron-specific CDK5 activator CDK5R1/p39NCK5A both share limited similarity to cyclins, and thus may define a distinct family of cyclin-dependent kinase activating proteins.The predicted 367-amino acid p39(nck5ai) protein shares 57% sequence identity with human NCK5A. As does p25(nck5a), a 30-kD truncated form of p39(nck5ai) activated both recombinant and native CDK5 in vitro. Northern blot analysis of rat tissues indicated that both Nck5A and p39(nck5ai) are expressed exclusively in brain. In situ hybridization to rat brain sections revealed that p39(nck5ai) mRNA was highly expressed in the CA1 to CA3 zone of hippocampal formation, an area highly enriched in neurons.