title: Amino acids at positions 3 and 4 determine the membrane specificity of Pseudomonas aeruginosa lipoproteins.
abstract: Escherichia coli lipoproteins with Asp at position 2 remain in the inner membrane, whereas those having other amino acids are targeted to the outer membrane by the Lol system. However, inner membrane lipoproteins without Asp at position 2 are found in other Gram-negative bacteria. MexA of Pseudomonas aeruginosa, an inner membrane-specific lipoprotein involved in multidrug efflux, has Gly at position 2. To identify the residue or region of MexA that functions as an inner membrane retention signal, we constructed chimeric lipoproteins comprising various regions of MexA and an outer membrane lipoprotein, OprM, and analyzed their membrane localization. Lys and Ser at positions 3 and 4, respectively, were found to be critical for the inner membrane localization of MexA in P. aeruginosa. Substitution of these residues with Leu and Ile, which are present in OprM, was sufficient to target the chimeric lipoprotein to the outer membrane and to abolish the ability of MexA to confer drug resistance. The membrane specificity of a model lipoprotein, lipoMalE, a lipidated variant of the periplasmic maltose-binding protein of E. coli, was also determined by the residues at positions 3 and 4 in P. aeruginosa. In contrast to the widely accepted "+2 rule" for E. coli lipoproteins, these results suggest a new "+3, +4 rule" for lipoprotein sorting in P. aeruginosa, namely, the final destination of lipoproteins is determined by the residues at positions 3 and 4.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Narita
authors.forename: Hajime
authors.initials: H
authors.lastname: Tokuda
mesh_terms: D000596:Amino Acids / Q000235:genetics / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D050506:Mutant Chimeric Proteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D000596:Amino Acids; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; D050506:Mutant Chimeric Proteins; C499290:OppA protein, E coli; C402263:OprM protein, Pseudomonas aeruginosa