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Introduction to Solid Supported Membrane Based Electrophysiology
Published on: May 11, 2013
The alternating access transport mechanism in LacY
H Ronald Kaback1, Irina Smirnova, Vladimir Kasho
1Department of Physiology, University of California Los Angeles, Los Angeles, CA 90095, USA. rkaback@mednet.ucla.edu
The Journal of Membrane Biology
|December 17, 2010
Summary
Lactose permease (LacY) in E. coli undergoes conformational changes for sugar transport. This review highlights biochemical and biophysical evidence supporting the alternating access mechanism for lactose and proton symport.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Lactose permease (LacY) from Escherichia coli is a key transporter protein.
- LacY facilitates the symport of lactose and protons across the cell membrane.
- The dynamic nature of LacY suggests a complex transport mechanism.
Purpose of the Study:
- To review biochemical and biophysical approaches providing evidence for the alternating access mechanism of LacY.
- To elucidate the conformational changes involved in lactose/H(+) symport.
- To honor Stephan H. White's contributions to the field.
Main Methods:
- Review of existing biochemical studies.
- Analysis of biophysical data.
- In camera examination of experimental evidence.
Main Results:
- Sugar binding induces significant conformational changes in LacY.
- Evidence supports a global conformational change mechanism.
- The transport involves alternating access of binding sites to either side of the membrane.
Conclusions:
- The alternating access model is strongly supported by experimental data for LacY.
- Lactose/H(+) symport likely occurs via a global conformational change.
- This mechanism explains the translocation of substrates across the membrane.
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