In vivo assessment of the Tat signal peptide specificity in Escherichia coli.
Tat- and Sec-targeting signal peptides are specific for the cognate Tat or Sec pathways. Using two reporter proteins, the specificity and convertibility of a Tat signal peptide were assessed in vivo. The specific substitutions by RK, KR and KK for the RR motif of the TorA signal peptide had no effect on the exclusive Tat-dependent export of colicin V (ColV). By introducing multiple substitutions in a typical Tat signal peptide, altered signal peptides lacking the twin-arginine motif were obtained. Interestingly, some of these signal peptides preserved Tat-pathway targeting capacity, but resulted in a loss of exclusivity. In addition, further increasing the hydrophobicity of the n-region without modifying the h-region converted the Tat signal peptides to Sec signal peptides in the ColV transport. Replacement of positively charged residues in the c-region also abolished the Tat-exclusive targeting of ColV or green fluorescent protein (GFP), but the folded GFP could be transported only through the Tat pathway. These results strongly suggest that the overall hydrophobicity of the n-region is one of the determinants of Tat-targeting exclusivity.
Ize
Bérengère
B
Laboratoire de Chimie Bactérienne, UPR 9043, Institut de Biologie Structurale et Microbiologie, CNRS, 31 chemin Joseph Aiguier, F-13402 Marseille cedex 20, France.
Gérard
Fabien
F
Wu
Long-Fei
LF
D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D057927:Hydrophobic and Hydrophilic Interactions; D008164:Luminescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport; D015398:Signal Transduction; D013045:Species Specificity
D008164:Luminescent Proteins; D021382:Protein Sorting Signals; D049452:Green Fluorescent Proteins