Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1808, Issue 10, Pages 2508-2516Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2011.07.017
Keywords
Solid supported membrane; Electrophysiology; Fluorescence spectroscopy; Kinetic model; Transport mechanism; Sugar transport
Categories
Funding
- Deutsche Forschungsgemeinschaft [SFB 807]
- Ministry of Education, Romania
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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. (C) 2011 Elsevier B.V. All rights reserved.
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