3ZK8 image
Entry Detail
PDB ID:
3ZK8
Keywords:
Title:
CRYSTAL STRUCTURE OF PNEUMOCOCCAL SURFACE ANTIGEN PSAA E205Q IN THE METAL-FREE, OPEN STATE
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2013-01-22
Release Date:
2013-11-06
Method Details:
Experimental Method:
Resolution:
1.65 Å
R-Value Free:
0.18
R-Value Work:
0.14
R-Value Observed:
0.15
Space Group:
P 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:MANGANESE ABC TRANSPORTER SUBSTRATE-BINDING LIPOPROTEIN
Mutations:YES
Chain IDs:A, B
Chain Length:278
Number of Molecules:2
Biological Source:STREPTOCOCCUS PNEUMONIAE
Ligand Molecules
Primary Citation

Abstact

The relative stability of divalent first-row transition metal ion complexes, as defined by the Irving-Williams series, poses a fundamental chemical challenge for selectivity in bacterial metal ion acquisition. Here we show that although the substrate-binding protein of Streptococcus pneumoniae, PsaA, is finely attuned to bind its physiological substrate manganese, it can also bind a broad range of other divalent transition metal cations. By combining high-resolution structural data, metal-binding assays and mutational analyses, we show that the inability of open-state PsaA to satisfy the preferred coordination chemistry of manganese enables the protein to undergo the conformational changes required for cargo release to the Psa permease. This is specific for manganese ions, whereas zinc ions remain bound to PsaA. Collectively, these findings suggest a new ligand binding and release mechanism for PsaA and related substrate-binding proteins that facilitate specificity for divalent cations during competition from zinc ions, which are more abundant in biological systems.

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Primary Citation of related structures