Chloroplast TatC plays a direct role in thylakoid (Delta)pH-dependent protein transport.
The thylakoid (Delta)pH-dependent pathway transports folded proteins. Identified components include Hcf106 and Tha4. Orthologs of these proteins plus a membrane protein called TatC are essential for the homologous bacterial Tat system. Here we report identification of a chloroplast TatC (cpTatC). cpTatC is an integral thylakoid membrane protein as determined by in vitro chloroplast import and immunoblotting. Antibody to cpTatC specifically inhibited the thylakoid (Delta)pH-dependent pathway in vitro. cpTatC is present in about the same quantity as estimated translocation sites, whereas Hcf106 and Tha4 are present in 5-8-fold excess. These results are relevant to mechanistic models for this system.
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Horticultural Sciences and Plant Molecular and Cellular Biology, Fifield Hall, University of Florida, Gainesville, FL 32611, USA.
Summer
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Cline
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D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015153:Blotting, Western; D003001:Cloning, Molecular; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000737:chemistry / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017510:Protein Folding; D021381:Protein Transport / Q000187:drug effects; D016415:Sequence Alignment; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism*
D000906:Antibodies; D008565:Membrane Proteins; D010940:Plant Proteins; C432107:TatC protein, plant