The Salmonella enterica ZinT structure, zinc affinity and interaction with the high-affinity uptake protein ZnuA provide insight into the management of periplasmic zinc.
Biochim Biophys Acta
; 1840(1): 535-44, 2014 Jan.
Article
em En
| MEDLINE
| ID: mdl-24128931
ABSTRACT
BACKGROUND:
In Gram-negative bacteria the ZnuABC transporter ensures adequate zinc import in Zn(II)-poor environments, like those encountered by pathogens within the infected host. Recently, the metal-binding protein ZinT was suggested to operate as an accessory component of ZnuABC in periplasmic zinc recruitment. Since ZinT is known to form a ZinT-ZnuA complex in the presence of Zn(II) it was proposed to transfer Zn(II) to ZnuA. The present work was undertaken to test this claim.METHODS:
ZinT and its structural relationship with ZnuA have been characterized by multiple biophysical techniques (X-ray crystallography, SAXS, analytical ultracentrifugation, fluorescence spectroscopy).RESULTS:
The metal-free and metal-bound crystal structures of Salmonella enterica ZinT show one Zn(II) binding site and limited structural changes upon metal removal. Spectroscopic titrations with Zn(II) yield a KD value of 22±2nM for ZinT, while those with ZnuA point to one high affinity (KD<20nM) and one low affinity Zn(II) binding site (KD in the micromolar range). Sedimentation velocity experiments established that Zn(II)-bound ZinT interacts with ZnuA, whereas apo-ZinT does not. The model of the ZinT-ZnuA complex derived from small angle X-ray scattering experiments points to a disposition that favors metal transfer as the metal binding cavities of the two proteins face each other.CONCLUSIONS:
ZinT acts as a Zn(II)-buffering protein that delivers Zn(II) to ZnuA. GENERALSIGNIFICANCE:
Knowledge of the ZinT-ZnuA relationship is crucial for understanding bacterial Zn(II) uptake.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Zinco
/
Salmonella enterica
/
Periplasma
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2014
Tipo de documento:
Article
País de afiliação:
Itália