Abstract
It has been suggested that the MexB subunit of the MexAB-OprM efflux transporter of Pseudomonas aeruginosa exports xenobiotics in an energy-dependent manner. To investigate the role of the transmembrane segments (TMS) of MexB in the transporter activity, we isolated 24 spontaneous mutants showing hypersusceptibility to antibiotics. Among them, three mutations were located at TMS-3, TMS-4, and TMS-10 having amino acid substitution Leu376vPro, Gly397vVal, and Val928vGly, respectively. A secondary mutation, which suppressed the defect caused by the Val928vGly mutation in TMS-10, was found at the 403rd amino acid residue in TMS-4 with a change of glycine to serine, suggesting that TMS-4 and TMS-10 may be in close proximity. This result provided strong support for the recent notion that negatively charged residues in TMS-4 might form a salt-bridge with a positive charge in TMS-10 (Guan, L., and Nakae, T. (2001) J. Bacteriol. 183, 1734-1739). The transporter function impaired by the Gly397vVal mutation in TMS-4 was recovered by the secondary mutation, Gln998vHis, in the loop between TMS-11 and TMS-12, thereby suggesting that TMS-4 and TMS-11 or TMS-12 might also be in close proximity. Thus, it is most likely that TMS-4, TMS-10, and T...Continue Reading
References
Nov 1, 1992·Proceedings of the National Academy of Sciences of the United States of America·M Sahin-TóthH R Kaback
Feb 25, 1991·Biochimica Et Biophysica Acta·S C KingT H Wilson
Aug 15, 1970·Nature·U K Laemmli
Jan 1, 1995·Microbiology and Immunology·T Nakae
May 16, 1995·Biochemical and Biophysical Research Communications·S R MorshedT Nakae
Dec 1, 1994·Trends in Microbiology·D MaH Nikaido
Nov 1, 1993·Molecular Microbiology·K PooleS Neshat
Apr 15, 1994·Science·H Nikaido
Aug 1, 1996·Microbiology·H Yoneyama, T Nakae
Dec 1, 1996·Microbiological Reviews·I T PaulsenR A Skurray
Apr 28, 1997·Biochemical and Biophysical Research Communications·H YoneyamaT Nakae
Aug 29, 1997·The Journal of Biological Chemistry·A OcaktanT Nakae
Oct 23, 1997·The Journal of Biological Chemistry·N J PazdernikR J Brooker
Apr 16, 1998·Biochemical and Biophysical Research Communications·H YoneyamaT Nakae
Apr 3, 1999·The Journal of Biological Chemistry·L GuanT Nakae
Feb 15, 2000·The Journal of Biological Chemistry·H YoneyamaT Nakae
Feb 19, 2000·Antimicrobial Agents and Chemotherapy·H MasedaT Nakae
Feb 13, 2001·Journal of Bacteriology·L Guan, T Nakae