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A structural basis for Mg2+ homeostasis and the CorA translocation cycle
1Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada. payandeh@uhnres.utoronto.ca
The EMBO Journal
|August 12, 2006
Summary
This study reveals the structure of the CorA magnesium transporter, showing how it senses and transports magnesium ions. It acts as a molecular switch, controlling magnesium homeostasis in cells.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Magnesium ions (Mg2+) are essential for numerous cellular processes.
- The CorA transporter is crucial for Mg2+ homeostasis.
- Understanding CorA's mechanism is key to comprehending cellular Mg2+ regulation.
Purpose of the Study:
- To elucidate the structural basis of Mg2+ transport by the CorA homologue from Thermotoga maritima.
- To identify the molecular mechanisms underlying Mg2+ selectivity and homeostasis.
- To characterize the divalent cation sensing capabilities of CorA.
Main Methods:
- X-ray crystallography at 3.7 A resolution to determine the structure of CorA in complex with divalent cations.
- Proteolytic protection assays to investigate protein stability and conformational changes.
- Biophysical analyses to characterize protein function.
- Comparative structural analysis with homologous proteins.
Main Results:
- The structure reveals 12 divalent cations bound to CorA, with one near the conserved GMN motif in the transmembrane region.
- The pore's selectivity filter may discriminate substrates based on size and hydration.
- A cytoplasmic funnel domain with ten metal sites acts as an intrinsic divalent cation sensor.
- CorA functions as a Mg2+-specific homeostatic molecular switch.
Conclusions:
- The CorA structure provides insights into the transport and selectivity mechanisms for divalent cations.
- The cytoplasmic sensor domain regulates transport activity, functioning as a molecular switch for Mg2+ homeostasis.
- This work illuminates the reaction coordinate for a diverse family of transport proteins.
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