The distribution of folates in plant cells suggests a complex traffic of the vitamin between the organelles and the cytosol. The Arabidopsis thaliana protein AtFOLT1 encoded by the At5g66380 gene is the closest homolog of the mitochondrial folate transporters (MFTs) characterized in mammalian cells. AtFOLT1 belongs to the mitochondrial carrier family, but GFP-tagging experiments and Western blot analyses indicated that it is targeted to the envelope of chloroplasts.
View Article and Find Full Text PDFG-protein-coupled receptor kinase 2 (GRK2) is activated by free Gbetagamma subunits. A Gbetagamma binding site of GRK2 is localized in the carboxyl-terminal pleckstrin homology domain. This Gbetagamma binding site of GRK2 also regulates Gbetagamma-stimulated signaling by sequestering free Gbetagamma subunits.
View Article and Find Full Text PDFSequences ranging from nucleotide positions -14 to +4 relative to the transcription start site constitute an in vitro functional pea atp9 promoter. A comparison of respective sequence segments surrounding 11 unambiguously identified transcription initiation sites of various dicotyledoneous plant species revealed the highest level of evolutionary fidelity of nucleotide identities within the conserved nonanucleotide motif (CNM), suggesting their importance for promoter function. Using a mitochondrial in vitro transcription system, a detailed analysis by site-directed mutagenesis now reveals that the alteration of nucleotides -6 to -2 and +1 within the CNM indeed reduces promoter activity by more than 80%.
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