Efficient twin arginine translocation (Tat) pathway transport of a precursor protein covalently anchored to its initial cpTatC binding site.
The thylakoid twin arginine protein translocation (Tat) system operates by a cyclical mechanism in which precursors bind to a cpTatC-Hcf106 receptor complex, which then recruits Tha4 to form the translocase. After translocation, the translocase disassembles. Here, we fine-mapped initial interactions between precursors and the components of the receptor complex. Precursors with (Tmd)Phe substitutions in the signal peptide and early mature domain were bound to thylakoids and photo-cross-linked to components. cpTatC and Hcf106 were found to interact with different regions of the signal peptide. cpTatC cross-linked strongly to residues in the immediate vicinity of the twin arginine motif. Hcf106 cross-linked less strongly to residues in the hydrophobic core and the early mature domain. To determine whether precursors must leave their initial sites of interaction during translocation, cross-linked precursors were subjected to protein transport conditions. tOE17 cross-linked to cpTatC was efficiently translocated, indicating that the mature domain of the precursor can be translocated while the signal peptide remains anchored to the receptor complex.
Gérard
Fabien
F
Horticultural Sciences Department and Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, Florida 32611, USA.
Cline
Kenneth
K
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001120:Arginine / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018532:Pisum sativum; D010649:Phenylalanine / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000235:genetics; D021381:Protein Transport / Q000235:genetics
C109236:Hcf106 protein, plant; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C432107:TatC protein, plant; D010649:Phenylalanine; D001120:Arginine