KIC, a novel Ca2+ binding protein with one EF-hand motif, interacts with a microtubule motor protein and regulates trichome morphogenesis.
Kinesin-like calmodulin binding protein (KCBP) is a microtubule motor protein involved in the regulation of cell division and trichome morphogenesis. Genetic studies have shown that KCBP is likely to interact with several other proteins. To identify KCBP-interacting proteins, we used the C-terminal region of KCBP in a yeast two-hybrid screen. ... This screening resulted in the isolation of a novel KCBP-interacting Ca2+ binding protein (KIC). KIC, with its single EF-hand motif, bound Ca2+ at a physiological concentration. Coprecipitation with bacterially expressed protein and native KCBP, gel-mobility shift studies, and ATPase assays with the KCBP motor confirmed that KIC interacts with KCBP in a Ca2+-dependent manner. Interestingly, although both Ca2+-KIC and Ca2+-calmodulin were able to interact with KCBP and inhibit its microtubule binding activity, the concentration of Ca2+ required to inhibit the microtubule-stimulated ATPase activity of KCBP by KIC was threefold less than that required for calmodulin. Two KIC-related Ca2+ binding proteins and a centrin from Arabidopsis, which contain one and four EF-hand motifs, respectively, bound Ca2+ but did not affect microtubule binding and microtubule-stimulated ATPase activities of KCBP, indicating the specificity of Ca2+ sensors in regulating their targets. Overexpression of KIC in Arabidopsis resulted in trichomes with reduced branch number resembling the zwichel/kcbp phenotype. These results suggest that KIC modulates the activity of KCBP in response to changes in cytosolic Ca2+ and regulates trichome morphogenesis.
Mesh Terms:
Adenosine Triphosphatases, Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Calcium, Calcium-Binding Proteins, Calmodulin, Calmodulin-Binding Proteins, Cell Surface Extensions, EF Hand Motifs, Gene Expression Regulation, Developmental, Gene Expression Regulation, Plant, Microtubule-Associated Proteins, Molecular Sequence Data, Phylogeny, Protein Interaction Mapping, Sequence Homology, Amino Acid
Adenosine Triphosphatases, Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Calcium, Calcium-Binding Proteins, Calmodulin, Calmodulin-Binding Proteins, Cell Surface Extensions, EF Hand Motifs, Gene Expression Regulation, Developmental, Gene Expression Regulation, Plant, Microtubule-Associated Proteins, Molecular Sequence Data, Phylogeny, Protein Interaction Mapping, Sequence Homology, Amino Acid
Plant Cell
Date: Jan. 01, 2004
PubMed ID: 14688294
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