4EEB

CorA coiled-coil mutant under Mg2+ absence

Summary for 4EEB

• Entry DOI: 10.2210/pdb4eeb/pdb
• Related: 2BBJ 2HN2 2IUB 4EED
• Descriptor: Magnesium transport protein CorA, CESIUM ION, SODIUM ION (3 entities in total)
• Functional Keywords: trans-membrane protein, coiled-coil, mg2+ channel, cesium binding, membrane, metal transport
• Biological source: Thermotoga maritima
• Cellular location: Cell inner membrane; Multi-pass membrane protein: Q9WZ31
• Total number of polymer chains: 5
• Total formula weight: 195854.21

Authors

Pfoh, R.,Pai, E.F. (deposition date: 2012-03-28, release date: 2012-11-14, Last modification date: 2023-09-13)

Primary citation

Pfoh, R.,Li, A.,Chakrabarti, N.,Payandeh, J.,Pomes, R.,Pai, E.F.
Structural asymmetry in the magnesium channel CorA points to sequential allosteric regulation.
Proc.Natl.Acad.Sci.USA, 109:18809-18814, 2012

PubMed Abstract: Magnesium ions (Mg(2+)) are essential for life, but the mechanisms regulating their transport into and out of cells remain poorly understood. The CorA-Mrs2-Alr1 superfamily of Mg(2+) channels represents the most prevalent group of proteins enabling Mg(2+) ions to cross membranes. Thermotoga maritima CorA (TmCorA) is the only member of this protein family whose complete 3D fold is known. Here, we report the crystal structure of a mutant in the presence and absence of divalent ions and compare it with previous divalent ion-bound TmCorA structures. With Mg(2+) present, this structure shows binding of a hydrated Mg(2+) ion to the periplasmic Gly-Met-Asn (GMN) motif, revealing clues of ion selectivity in this unique channel family. In the absence of Mg(2+), TmCorA displays an unexpected asymmetric conformation caused by radial and lateral tilts of protomers that leads to bending of the central, pore-lining helix. Molecular dynamics simulations support these movements, including a bell-like deflection. Mass spectrometric analysis confirms that major proteolytic cleavage occurs within a region that is selectively exposed by such a bell-like bending motion. Our results point to a sequential allosteric model of regulation, where intracellular Mg(2+) binding locks TmCorA in a symmetric, transport-incompetent conformation and loss of intracellular Mg(2+) causes an asymmetric, potentially influx-competent conformation of the channel.

PubMed: 23112165
DOI: 10.1073/pnas.1209018109

Experimental method

X-RAY DIFFRACTION (3.8 Å)