Abstract
The cell cycle in plants, as in eukaryotes, is regulated by cyclin-dependent kinases (CDKs). CDK activity is controlled by various regulatory factors during the cell cycle and CDK inhibitors play a major role in controlling the G1/S transition through the control of CDK activity. Analysis of the complete Arabidopsis genome revealed the presence of seven genes belonging to CDK inhibitor, designated Kip-related proteins (KRPs). These genes encode proteins with distant sequence homology with an animal CDK inhibitor p27Kip1. In this study, the function of KRP protein was analyzed in terms of an interaction with Cyclin/CDK.
With the exception of KRP7, all KRPs interact with Cyclin/CDK complexes but none interact with Cyclin and CDK protein alone using in vitro binding assay. We have purified three recombinant KRP proteins from E. coli. These proteins inhibit kinase activity of CyclinD2/Cdc2a complex, which is purified from insect cells, in a different dose-dependent manner.
