Cleavage, methylation, and localization of the Pseudomonas aeruginosa export proteins XcpT, -U, -V, and -W.
Four components of the apparatus of extracellular protein secretion of Pseudomonas aeruginosa, Xcpt, -U, -V, and -W (XcpT-W), are synthesized as precursors with short N-terminal leader peptides that share sequence similarity with the pilin subunit of this organism. A specialized leader peptidase/methylase, product of the pilD gene, has been shown to cleave the leader peptide from prepilin and to methylate the N-terminal phenylalanine of the mature pilin. Antibodies were prepared against XcpT-W and used to purify each of these proteins. Sequence analysis of XcpT-W has shown that these proteins, like mature pilin, contain N-methylphenylalanine as the N-terminal amino acid. Analysis of cellular fractions from wild-type and pilD mutant strains of P. aeruginosa showed that the precursor forms of XcpT-W are located predominantly in the bacterial inner membrane, and their localization is not altered after PilD-mediated removal of the leader sequence. These studies demonstrate that the biogenesis of the apparatus of extracellular protein secretion and that of type IV pili share a requirement for PilD. This bifunctional enzyme, acting in the inner membrane, cleaves the leader peptides from precursors of pilins and XcpT-W and subsequently methylates the amino group of the N-terminal phenylalanine of each of its substrates.
Nunn
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DN
Department of Microbiology, University of Illinois, Urbana 61801.
Lory
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S
D000595:Amino Acid Sequence; D000906:Antibodies; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D036781:Fimbriae Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008745:Methylation; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000302:isolation & purification / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping
D000906:Antibodies; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C082104:XcpT protein, Pseudomonas aeruginosa; C082105:XcpU protein, Pseudomonas aeruginosa; C082106:XcpV protein, Pseudomonas aeruginosa; C082107:XcpW protein, Pseudomonas aeruginosa; D036781:Fimbriae Proteins