Magnesium transporters: properties, regulation and structure

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Magnesium ion (Mg2+) chemistry is unique among biological cations, influencing transport system properties.
• Prokaryotes utilize three main Mg2+ transport systems: CorA, MgtA/B, and MgtE, with varying distribution across Eubacteria and Archaea.
• Eukaryotic Mg2+ transporters include mitochondrial Mrs2p channels, fungal ALR proteins (CorA homologs), and SLC41 transporters (MgtE homologs).

Purpose of the Study:

• To review the diverse classes of Mg2+ transport systems in prokaryotes and eukaryotes.
• To detail the structural and mechanistic insights into the CorA Mg2+ transporter.
• To discuss the physiological implications and regulation of Mg2+ transport.

Main Methods:

• Comparative analysis of Mg2+ transporter sequences across different domains of life.
• Review of existing structural data, particularly for the CorA transporter.
• Discussion of genetic studies, such as corA mutations in Salmonella Typhimurium.

Main Results:

• CorA is the only Mg2+ transporter with solved structure, revealing a homopentameric architecture with a transmembrane ion conduction pathway.
• Mg2+ transport via CorA involves cation binding, passage through transmembrane domains without electrostatic interactions, and regulation by cytosolic domains.
• CorA and MgtE are likely housekeeping genes, as they are not transcriptionally regulated, though corA mutations can affect virulence.

Conclusions:

• Mg2+ transport systems exhibit diverse structures and mechanisms reflecting Mg2+ unique chemistry.
• The CorA transporter's structure provides key insights into biological cation transport.
• Despite being housekeeping genes, Mg2+ transporters like CorA play roles in bacterial virulence and cellular homeostasis.