[show abstract][hide abstract] ABSTRACT: The plant mitochondrial DNA-binding protein ODB1 was identified from a mitochondrial extract after DNA-affinity purification. ODB1 (organellar DNA-binding protein 1) co-purified with WHY2, a mitochondrial member of the WHIRLY family of plant-specific proteins involved in the repair of organellar DNA. The Arabidopsis thaliana ODB1 gene is identical to RAD52-1, which encodes a protein functioning in homologous recombination in the nucleus but additionally localizing to mitochondria. We confirmed the mitochondrial localization of ODB1 by in vitro and in vivo import assays, as well as by immunodetection on Arabidopsis subcellular fractions. In mitochondria, WHY2 and ODB1 were found in large nucleo-protein complexes. Both proteins co-immunoprecipitated in a DNA-dependent manner. In vitro assays confirmed DNA binding by ODB1 and showed that the protein has higher affinity for single-stranded than for double-stranded DNA. ODB1 showed no sequence specificity in vitro. In vivo, DNA co-immunoprecipitation indicated that ODB1 binds sequences throughout the mitochondrial genome. ODB1 promoted annealing of complementary DNA sequences, suggesting a RAD52-like function as a recombination mediator. Arabidopsis odb1 mutants were morphologically indistinguishable from the wild-type, but following DNA damage by genotoxic stress, they showed reduced mitochondrial homologous recombination activity. Under the same conditions, the odb1 mutants showed an increase in illegitimate repair bypasses generated by microhomology-mediated recombination. These observations identify ODB1 as a further component of homologous recombination-dependent DNA repair in plant mitochondria.
[show abstract][hide abstract] ABSTRACT: The 14-3-3 proteins are a family of highly conserved proteins found in all eukaryotes - from the yeasts to mammals. They regulate several cellular processes recognizing unique conservative, mostly phosphorylated motif of partner proteins. Binding of the 14-3-3 proteins regulates their partners through a variety of mechanisms, such as altering their catalytic activity, subcellular localization, stability or altering their interactions with other protein molecules. The native 14-3-3 proteins are present in form of homo- and hetero-dimers. The most structurally variable N-and C-termini are responsible for isoform specific protein-protein interactions, and cellular localization. In plant cell, 14-3-3 proteins appear to play an important role in regulation of key enzymes of carbon and nitrogen metabolism, modulation ion pumps and channels. They are also involved in signal transduction pathways and even in gene expression.
[show abstract][hide abstract] ABSTRACT: Purified cauliflower (Brassica oleracea var. botrytis) mitochondrial proteins fractionated into soluble, membrane, integral membrane and peripheral membrane samples were analyzed
by 2D- PAGE (isoelectric focusing/ SDS polyacrylamide gel electrophoresis). 2D gels patterns were compared using the Imager
Master 2D Elite software. 561 silver stained protein spots were resolved after electrophoresis under standard conditions of
a whole protein extract. In the soluble fraction a prevalent number of more intense protein spots was observed. The cauliflower
protein 2D patterns resembled Arabidopsis thaliana 2D patterns. The two protein spots selected which occupied a similar isoelectric point positions on both gels represented
the same proteins as revealed by ESI-MS analysis of cauliflower proteins. The third selected spot belongs to unidentified
proteins. The comparative analysis of mitochondrial suborganellar fractions proved the usefulness of this approach.
Acta Physiologiae Plantarum 01/2005; 27(3):275-281. · 1.31 Impact Factor