Quantification of Cyclin-CDK dissociation constants using FCCS with green and near-infrared fluorescent proteins.
The cell cycle is a highly coordinated process governed by cyclin-bound cyclin-dependent kinases (CDKs). While the interaction between cyclin and CDK are well-documented, the dissociation constants (Kd) between specific cyclin-CDK pairs within living cells remain poorly understood. Fluorescence cross-correlation spectroscopy (FCCS) enables the quantification of the Kd, but challenges remain in selecting an optimal pair of fluorescent molecules for FCCS in a living cell. In this study, we demonstrate that mNeonGreen and phycocyanobilin-bound miRFP670 represent a suitable pair for FCCS in living cells from the viewpoint of high photostability and low bleed-through. This fluorescent protein pair enables us to measure the Kd values of the cyclin-dependent kinase Cdc2 and B-type cyclin Cdc13 in fission yeast cells. Moreover, we roughly estimated the Kd values for 36 cyclin-CDK complexes, formed by 9 distinct cyclins and 4 CDKs, in mammalian cells, including unconventional cyclin-CDK pairs. These measurements suggest potential versatility of cyclin-CDK binding in cell cycle progression, with implications for understanding cell cycle regulation in both fission yeast and higher eukaryotes.
Toyama A, Goto Y, Yamauchi Y, Sugiyama H, Kondo Y, Mochizuki A, Aoki K