title: Comparative modeling of the three-dimensional structure of the calmodulin-related TCH2 protein from Arabidopsis.
abstract: Plants adapt to various stresses by developmental alterations that render them less easily damaged. Expression of the TCH2 gene of Arabidopsis is strongly induced by stimuli such as touch and wind. The gene product, TCH2, belongs to the calmodulin (CaM) family of proteins and contains four highly conserved Ca(2+)-binding EF-hands. We describe here the structure of TCH2 in the fully Ca(2+)-saturated form, constructed using comparative molecular modeling, based on the x-ray structure of paramecium CaM. Like known CaMs, the overall structure consists of two globular domains separated by a linker helix. However, the linker region has added flexibility due to the presence of 5 glycines within a span of 6 residues. In addition, TCH2 is enriched in Lys and Arg residues relative to other CaMs, suggesting a preference for targets which are more negatively charged. Finally, a pair of Cys residues in the C-terminal domain, Cys126 and Cys131, are sufficiently close in space to form a disulfide bridge. These predictions serve to direct future biochemical and structural studies with the overall aim of understanding the role of TCH2 in the cellular response of Arabidopsis to environmental stimuli.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Canada.
authors.forename: A R
authors.initials: AR
authors.lastname: Khan
authors.forename: K A
authors.initials: KA
authors.lastname: Johnson
authors.forename: J
authors.initials: J
authors.lastname: Braam
authors.forename: M N
authors.initials: MN
authors.lastname: James
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000737:chemistry*; D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D010940:Plant Proteins; C106145:TCH2 protein, Arabidopsis