Role of the Pseudomonas aeruginosa PlcH Tat signal peptide in protein secretion, transcription, and cross-species Tat secretion system compatibility.
The secretion of PlcH and its homolog PlcN of Pseudomonas aeruginosa through the inner membrane depends upon a functional twin arginine translocase (Tat) system and a Tat signal sequence. Conserved twin arginine (Arg) residues within the Tat signal sequence consensus motif (S/TRRxFLK) are considered essential for the secretion of Tat substrates, but some exceptions (e.g., Lys and Arg) to the twin Arg residues in this motif have been noted. The roles of all three Arg residues within the PlcH RRRTFLK consensus motif were examined. Data are presented which indicate that Arg-9 and Arg-10 are essential for PlcH secretion across the inner membrane, but the mutation of Arg-8 (e.g., to Ala or Ser) had no observable effect on the localization of PlcH. In the signal sequence of PlcH and in all of its homologs in other bacteria, there are basic amino acid residues (Arg, Lys, and Gln) immediately adjacent to the signal peptidase cleavage site (Ala-X-Ala) that are not seen in Sec-dependent signal sequences. The mutation of these basic residues to Ala caused slightly decreased levels of extracellular PlcH, but normal localization was still observed. Deletion of the entire Tat signal sequence of PlcH not only resulted in the absence of detectable extracellular PlcH activity and protein but also caused a substantial decrease in the detectable level of plcH mRNA. Finally, data are presented which indicate that P. aeruginosa PlcH exhibits cross-species compatibility with the Escherichia coli Tat secretion machinery, but only when the E. coli Tat machinery is expressed in a P. aeruginosa host.
Snyder
Aleksandra
A
Department of Microbiology, Fitzsimons Mail Stop 8333, P.O. Box 6511, 12800 East 19th Ave., Aurora, CO 80045, USA.
Vasil
Adriana I
AI
Zajdowicz
Sheryl L
SL
Wilson
Zachary R
ZR
Vasil
Michael L
ML
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D016384:Consensus Sequence; D026901:Membrane Transport Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D013045:Species Specificity; D014158:Transcription, Genetic; D017855:Transferases (Other Substituted Phosphate Groups) / Q000737:chemistry / Q000378:metabolism*
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D017855:Transferases (Other Substituted Phosphate Groups); C477519:sphingomyelin synthase, Pseudomonas aeruginosa