title: Two maize Kip-related proteins differentially interact with, inhibit and are phosphorylated by cyclin D-cyclin-dependent kinase complexes.
abstract: The family of maize Kip-related proteins (KRPs) has been studied and a nomenclature based on the relationship to rice KRP genes is proposed. Expression studies of KRP genes indicate that all are expressed at 24 h of seed germination but expression is differential in the different tissues of maize plantlets. Recombinant KRP1;1 and KRP4;2 proteins, members of different KRP classes, were used to study association to and inhibitory activity on different maize cyclin D (CycD)-cyclin-dependent kinase (CDK) complexes. Kinase activity in CycD2;2-CDK, CycD4;2-CDK, and CycD5;3-CDK complexes was inhibited by both KRPs; however, only KRP1;1 inhibited activity in the CycD6;1-CDK complex, not KRP4;2. Whereas KRP1;1 associated with either CycD2;2 or CycD6;1, and to cyclin-dependent kinase A (CDKA) recombinant proteins, forming ternary complexes, KRP4;2 bound CDKA and CycD2;2 but did not bind CycD6;1, establishing a differential association capacity. All CycD-CDK complexes included here phosphorylated both the retinoblastoma-related (RBR) protein and the two KRPs; interestingly, while KRP4;2 phosphorylated by the CycD2;2-CDK complex increased its inhibitory capacity, when phosphorylated by the CycD6;1-CDK complex the inhibitory capacity was reduced or eliminated. Evidence suggests that the phosphorylated residues in KRP4;2 may be different for every kinase, and this would influence its performance as a cyclin-CDK inhibitor.
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.
authors.forename: Silvia K
authors.initials: SK
authors.lastname: Godínez-Palma
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.|I. Medizinische Klinik and Poliklinik, Universitätsmedizin der Johannes Gutenberg-Universität Mainz Obere Zahlbacherstr. 63 55131 Mainz, Germany.
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Rosas-Bringas
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.
authors.forename: Omar G
authors.initials: OG
authors.lastname: Rosas-Bringas
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.
authors.forename: Elpidio
authors.initials: E
authors.lastname: García-Ramírez
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.|Department of Plant Sciences, Plant Developmental Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Jorge
authors.initials: J
authors.lastname: Zamora-Zaragoza
authors.affiliation: Facultad de Química, Departamento de Bioquímica, UNAM, Avenida Universidad y Copilco, México DF 04510, México.
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Vázquez-Ramos
mesh_terms: D056741:Cyclin D / Q000235:genetics* / Q000378:metabolism; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics* / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D056741:Cyclin D; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D010940:Plant Proteins; D018844:Cyclin-Dependent Kinases
keywords: CDKs; ICK/KRPs; KRP phosphorylation; Zea mays.; cyclins D; kinase inhibition