title: Identification of CP12 as a Novel Calcium-Binding Protein in Chloroplasts.
abstract: Calcium plays an important role in the regulation of several chloroplast processes. However, very little is still understood about the calcium fluxes or calcium-binding proteins present in plastids. Indeed, classical EF-hand containing calcium-binding proteins appears to be mostly absent from plastids. In the present study we analyzed the stroma fraction of Arabidopsis chloroplasts for the presence of novel calcium-binding proteins using 2D-PAGE separation followed by calcium overlay assay. A small acidic protein was identified by mass spectrometry analyses as the chloroplast protein CP12 and the ability of CP12 to bind calcium was confirmed with recombinant proteins. CP12 plays an important role in the regulation of the Calvin-Benson-Bassham Cycle participating in the assembly of a supramolecular complex between phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase, indicating that calcium signaling could play a role in regulating carbon fixation.
authors.affiliation: Department of Biology I, LMU Munich, Großhaderner Street 2-4, D-82152 Planegg-Martinsried, Germany. rocha@bio.lmu.de.
authors.forename: Agostinho Gomes
authors.initials: AG
authors.lastname: Rocha
authors.affiliation: Department of Biology I, LMU Munich, Großhaderner Street 2-4, D-82152 Planegg-Martinsried, Germany. vothknecht@bio.lmu.de.|Center for Integrated Protein Science (Munich) at the Department of Biology of the LMU Munich, D-81377 Munich, Germany. vothknecht@bio.lmu.de.
authors.forename: Ute C
authors.initials: UC
authors.lastname: Vothknecht
keywords: CP12; Calvin-Benson-Bassham Cycle; calcium signaling; chloroplast