title: The Arabidopsis calmodulin-like proteins AtCML30 and AtCML3 are targeted to mitochondria and peroxisomes, respectively.
abstract: Calmodulin (CaM) is a ubiquitous sensor/transducer of calcium signals in eukaryotic organisms. While CaM mediated calcium regulation of cytosolic processes is well established, there is growing evidence for the inclusion of organelles such as chloroplasts, mitochondria and peroxisomes into the calcium/calmodulin regulation network. A number of CaM-binding proteins have been identified in these organelles and processes such as protein import into chloroplasts and mitochondria have been shown to be governed by CaM regulation. What have been missing to date are the mediators of this regulation since no CaM or calmodulin-like protein (CML) has been identified in any of these organelles. Here we show that two Arabidopsis CMLs, AtCML3 and AtCML30, are localized in peroxisomes and mitochondria, respectively. AtCML3 is targeted via an unusual C-terminal PTS1-like tripeptide while AtCML30 utilizes an N-terminal, non-cleavable transit peptide. Both proteins possess the typical structure of CaMs, with two pairs of EF-hand motifs separated by a short linker domain. They furthermore display common characteristics, such as calcium-dependent alteration of gel mobility and calcium-dependent exposure of a hydrophobic surface. This indicates that they can function in a similar manner as canonical CaMs. The presence of close homologues to AtCML3 and AtCML30 in other plants further indicates that organellar targeting of these CMLs is not a specific feature of Arabidopsis. The identification of peroxisomal and mitochondrial CMLs is an important step in the understanding how these organelles are integrated into the cellular calcium/calmodulin signaling pathways.
authors: Department of Biology of the LMU Munich, Center for Integrated Protein Science (Munich), 82152 Martinsried, Germany.
authors: Fatima
authors: F
authors: Chigri
authors: Sandra
authors: S
authors: Flosdorff
authors: Sahra
authors: S
authors: Pilz
authors: Eva
authors: E
authors: Kölle
authors: Esther
authors: E
authors: Dolze
authors: Christine
authors: C
authors: Gietl
authors: Ute C
authors: UC
authors: Vothknecht
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001693:Biological Transport, Active; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D052139:Intracellular Calcium-Sensing Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D020675:Peroxisomes / Q000378:metabolism; D010802:Phylogeny; D030821:Plants, Genetically Modified; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; C585826:CML3 protein, Arabidopsis; D002147:Calmodulin; D052139:Intracellular Calcium-Sensing Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C054562:yellow fluorescent protein, Bacteria