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Energy transduction in transmembrane ion pumps
Marc T Facciotti1, Shahab Rouhani-Manshadi, Robert M Glaeser
1Institute for Systems Biology, 1441 North 34th Street, Seattle, WA 98103, USA.
Trends in Biochemical Sciences
|September 15, 2004
Summary
New crystallographic structures reveal how ion pumps use buried counter ions to move ions across membranes. These ions are crucial for recruiting, binding, and transporting ions, enabling energy transduction.
Area of Science:
- Biochemistry
- Structural Biology
- Membrane Transport
Background:
- Ion pumps are essential molecular machines that transport ions across cell membranes against electrochemical gradients.
- Understanding their mechanism is key to comprehending cellular energy management and function.
Purpose of the Study:
- To elucidate the molecular mechanisms of ion pumping using recent crystallographic data.
- To investigate the role of buried counter ions in ion transport and energy transduction.
Main Methods:
- Analysis of recent crystallographic structures of three distinct ion pumps.
- Structural interpretation of ion binding, conformational changes, and energy transduction pathways.
Main Results:
- Structures reveal central roles for buried counter ions in substrate recruitment, binding, and energy transduction.
- Counter ions facilitate substrate ion binding by lowering the Born energy cost in the membrane interior.
- Ligand-induced conformational changes and charged gate formation prevent ion backflow.
Conclusions:
- Buried counter ions are critical for the entire ion pumping cycle, from substrate binding to release.
- These ions couple external energy input to charge separation, modulating substrate binding affinity.
- The findings provide a mechanistic view of how ion pumps function as molecular machines.