Topological analysis of an RND family transporter, MexD of Pseudomonas aeruginosa

FEBS Lett. 1999 Sep 10;458(1):32-6. doi: 10.1016/s0014-5793(99)01116-3.


The membrane topology of a resistance-nodulation-division (RND) family transporter, MexD of Pseudomonas aeruginosa, was determined. Although it had been predicted previously that most RND proteins contain 12 transmembrane helices, three independent computer programs used in the present study predicted that MexD possessed 11, 14 or 17 transmembrane segments. To investigate the topology of MexD more thoroughly, 25 MexD-PhoA (alkaline phosphatase) and 18 MexD-Bla (beta-lactamase) fusion plasmids were constructed and analyzed. The resulting topological model had just 12 transmembrane helices and two periplasmic loops of about 300 residues between helices 1 and 2 and helices 7 and 8. It is therefore proposed that the N- and C-termini are located in the cytoplasm and the predicted orientation is consistent with the 'positive-inside rule'. This topological model can be applied to other RND proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaline Phosphatase / chemistry
  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / genetics*
  • Biological Transport
  • Blotting, Western
  • Carrier Proteins / chemistry
  • Computer Simulation
  • Membrane Proteins / chemistry*
  • Models, Biological
  • Molecular Sequence Data
  • Plasmids / chemistry
  • Protein Conformation
  • Protein Structure, Secondary
  • Pseudomonas aeruginosa / chemistry*
  • Recombinant Fusion Proteins / chemistry
  • beta-Lactamases / chemistry


  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Membrane Proteins
  • MexD protein, Pseudomonas aeruginosa
  • Recombinant Fusion Proteins
  • Alkaline Phosphatase
  • beta-Lactamases