Structural and thermodynamic insights into a novel Mg2+ – citrate-binding protein from the ABC transporter superfamily

This study reports crystal structures of an Mg2+ – citrate-binding protein (MctA) from the Gram-negative thermophilic bacterium Thermus thermophilus HB8 in both apo and holo forms in the resolution range 1.63 – 2.50   Å . Despite binding various divalent metal ions, MctA possesses the coordination geometry to bind its physiological metal ion, Mg2+. The results also suggest an extended subclassification of cluster D SBPs, which are known to bind and transport divalent-metal-ion-complexed citrate molecules. Comparative assessment of the open and closed conformations of the wild-type and mutant MctA proteins suggests a gating mechanism of ligand entry following an `asymmetric domain movement' of the N-terminal domain for substrate binding.
Source: Acta Crystallographica Section D - Category: Biochemistry Authors: Tags: Gram-negative bacteria Thermus thermophilus HB8 nucleotide-binding domain secondary transporters ABC transporters substrate-binding proteins symporters Mg2 metal ions citrate research papers Source Type: research