1. Biochemical characterization of the histidine triad protein PhtD as a cell surface zinc-binding protein of pneumococcus.
- Author
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Loisel E, Chimalapati S, Bougault C, Imberty A, Gallet B, Di Guilmi AM, Brown J, Vernet T, and Durmort C
- Subjects
- Amino Acid Motifs, Bacterial Proteins chemistry, Carrier Proteins chemistry, Cation Transport Proteins chemistry, Hydrolases chemistry, Lipoproteins chemistry, Lipoproteins metabolism, Recombinant Proteins chemistry, Bacterial Proteins metabolism, Carrier Proteins metabolism, Cation Transport Proteins metabolism, Hydrolases metabolism, Streptococcus pneumoniae metabolism, Zinc metabolism
- Abstract
Zinc homeostasis is critical for pathogen host colonization. Indeed, during invasion, Streptococcus pneumoniae has to finely regulate zinc transport to cope with a wide range of Zn(2+) concentrations within the various host niches. AdcAII was identified as a pneumococcal Zn(2+)-binding protein; its gene is present in an operon together with the phtD gene. PhtD belongs to the histidine triad protein family, but to date, its function has not been clarified. Using several complementary biochemical methods, we provide evidence that like AdcAII, PhtD is a metal-binding protein specific for zinc. When Zn(2+) binds (K(d) = 131 ± 10 nM), the protein displays substantial thermal stabilization. We also present the first direct evidence of a joint function of AdcAII and PhtD by demonstrating that their expression is corepressed by Zn(2+), that they interact directly in vitro, and that they are colocalized at the bacterial surface. These results suggest the common involvement of the AdcAII-PhtD system in pneumococcal zinc homeostasis.
- Published
- 2011
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