title: Arabidopsis calmodulin-binding protein IQ67-domain 1 localizes to microtubules and interacts with kinesin light chain-related protein-1.
abstract: Calcium (Ca(2+)) is a key second messenger in eukaryotes and regulates diverse cellular processes, most notably via calmodulin (CaM). In Arabidopsis thaliana, IQD1 (IQ67 domain 1) is the founding member of the IQD family of putative CaM targets. The 33 predicted IQD proteins share a conserved domain of 67 amino acids that is characterized by a unique arrangement of multiple CaM recruitment motifs, including so-called IQ motifs. Whereas IQD1 has been implicated in the regulation of defense metabolism, the biochemical functions of IQD proteins remain to be elucidated. In this study we show that IQD1 binds to multiple Arabidopsis CaM and CaM-like (CML) proteins in vitro and in yeast two-hybrid interaction assays. CaM overlay assays revealed moderate affinity of IQD1 to CaM2 (K(d) ∼ 0.6 μm). Deletion mapping of IQD1 demonstrated the importance of the IQ67 domain for CaM2 binding in vitro, which is corroborated by interaction of the shortest IQD member, IQD20, with Arabidopsis CaM/CMLs in yeast. A genetic screen of a cDNA library identified Arabidopsis kinesin light chain-related protein-1 (KLCR1) as an IQD1 interactor. The subcellular localization of GFP-tagged IQD1 proteins to microtubules and the cell nucleus in transiently and stably transformed plant tissues (tobacco leaves and Arabidopsis seedlings) suggests direct interaction of IQD1 and KLCR1 in planta that is supported by GFP∼IQD1-dependent recruitment of RFP∼KLCR1 and RFP∼CaM2 to microtubules. Collectively, the prospect arises that IQD1 and related proteins provide Ca(2+)/CaM-regulated scaffolds for facilitating cellular transport of specific cargo along microtubular tracks via kinesin motor proteins.
authors.affiliation: Department of Molecular Signal Processing, Leibniz Institute of Plant Biochemistry, D-06120 Halle, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Bürstenbinder
authors.forename: Tatyana
authors.initials: T
authors.lastname: Savchenko
authors.forename: Jens
authors.initials: J
authors.lastname: Müller
authors.forename: Aaron W
authors.initials: AW
authors.lastname: Adamson
authors.forename: Gina
authors.initials: G
authors.lastname: Stamm
authors.forename: Raymond
authors.initials: R
authors.lastname: Kwong
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Zipp
authors.forename: Dhurvas Chandrasekaran
authors.initials: DC
authors.lastname: Dinesh
authors.forename: Steffen
authors.initials: S
authors.lastname: Abel
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D016547:Kinesins; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; C503424:IQD1 protein, Arabidopsis; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D016547:Kinesins; D002118:Calcium