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Updated: Jul 13, 2026

Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Conformational change in an MFS protein: MD simulations of LacY
John Holyoake1, Mark S P Sansom
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
Abstract:
Molecular dynamics simulations of lactose permease (LacY) in a phospholipid bilayer reveal the conformational dynamics of the protein. In inhibitor-bound simulations (i.e., those closest to the X-ray structure) the protein was stable, showing little conformational change over a 50 ns timescale. Movement of the bound inhibitor, TDG, to an alternative binding mode was observed, so that it interacted predominantly with the N-terminal domain and with residue E269 from the C-terminal domain. In multiple ligand-free simulations, a degree of domain closure occurred. This switched LacY to a state with a central cavity closed at both the intracellular and periplasmic ends. This may resemble a possible intermediate in the transport mechanism. Domain closure occurs by a combination of rigid-body movements of domains and of intradomain motions of helices, especially TM4, TM5, TM10, and TM11. A degree of intrahelix flexibility appears to be important in the conformational change.
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