Cdc37: a protein kinase chaperone?

The activity of most protein kinases is highly regulated, typically via phosphorylation and/or subunit association. However, the folding of protein kinases into an active state or a form capable of activation is now emerging as another important step through which they can be regulated. The 50-kDa protein Cdc37 and the associated heat-shock protein Hsp90 have been found to bind to, and be required for the activity of, diverse protein kinases, including Cdk4, v-Src, Raf and SEVENLESS. Together, Cdc37 and Hsp90 may act as a general chaperone for protein kinases, in particular those involved in signal-transduction pathways and cell-cycle control.