Arabidopsis KRPs have distinct inhibitory activity toward cyclin D2-associated kinases, including plant-specific B-type cyclin-dependent kinase

Arabidopsis contains seven Kip-related protein (KRP) genes encoding CDK (cychn-dependent kinase) inhibitors (CKIs), which shares a restricted similarity with mammalian P27(Kip1). Here, we analyze the characteristics of the KRPs. Although KRP1-KRP7 interact with active cyclin D2 (CYCD2)/CDKA and CYCD2/CDKB complexes to a similar extent, they inhibit kinase activity to a different extent. Our results suggest that inhibitory activity is related to the binding ability between KRP proteins and cyctin/CDK complexes, but secondary and tertiary structure may be also involved. These data provide the first evidence that KRPs inhibit kinase activity associated with plant-specific CDKB. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.