2011 - G117C MelB, a mutant melibiose permease with a changed conformational equilibrium

Icon N1  SURFE²R-technology (custom-built system) publication in Biochimica et Biophysica Acta (BBA) - Biomembranes (2011)

Ganea C., Meyer-Lipp K., Lemonnier R., Krah A., Leblanc G., Fendler K.

Biochimica et Biophysica Acta (BBA) - Biomembranes (2011) 1808(10):2508-2516


  • Steady-state kinetics of G117C MelB like wild type.
  • Pre steady-state kinetics altered in G117C MelB.
  • Initial configuration of G117C MelB differs from wild type.
  • Rapid dynamic equilibrium of substrate free transporter.


Replacement of the glycine at position 117 by a cysteine in the melibiose permease creates an interesting phenotype: while the mutant transporter shows still transport activity comparable to the wild type its pre steady-state kinetic properties are drastically altered. The transient charge displacements after substrate concentration jumps are strongly reduced and the fluorescence changes disappear. Together with its maintained transport activity this indicates that substrate translocation in G117C melibiose permease is not impaired but that the initial conformation of the mutant transporter differs from that of the wild type permease. A kinetic model for the G117C melibiose permease based on a rapid dynamic equilibrium of the substrate free transporter is proposed. Implications of the kinetic model for the transport mechanism of the wild type permease are discussed.

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