title: Differential transit peptide recognition during preprotein binding and translocation into flowering plant plastids.
abstract: Despite the availability of thousands of transit peptide (TP) primary sequences, the structural and/or physicochemical properties that determine TP recognition by components of the chloroplast translocon are not well understood. By combining a series of in vitro and in vivo experiments, we reveal that TP recognition is determined by sequence-independent interactions and vectorial-specific recognition domains. Using both native and reversed TPs for two well-studied precursors, small subunit of ribulose-1,5-bis-phosphate carboxylase/oxygenase, and ferredoxin, we exposed these two modes of recognition. Toc34 receptor (34-kD subunit of the translocon of the outer envelope) recognition in vitro, preprotein binding in organellar, precursor binding in vivo, and the recognition of TPs by the major stromal molecular motor Hsp70 are specific for the physicochemical properties of the TP. However, translocation in organellar and in vivo demonstrates strong specificity to recognition domain organization. This organization specificity correlates with the N-terminal placement of a strong Hsp70 recognition element. These results are discussed in light of how individual translocon components sequentially interact with the precursor during binding and translocation and helps explain the apparent lack of sequence conservation in chloroplast TPs.
authors: Graduate School of Genome Science and Technology, University of Tenessee, Knoxville, TN 37996, USA.
authors: Prakitchai
authors: P
authors: Chotewutmontri
authors: L Evan
authors: LE
authors: Reddick
authors: David R
authors: DR
authors: McWilliams
authors: Ian M
authors: IM
authors: Campbell
authors: Barry D
authors: BD
authors: Bruce
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D019295:Computational Biology; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D019684:Magnoliopsida / Q000201:enzymology / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000201:enzymology / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D018087:Plastids / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D014026:Nicotiana / Q000201:enzymology / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D005288:Ferredoxins; D010455:Peptides; D010940:Plant Proteins; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D012273:Ribulose-Bisphosphate Carboxylase