Biochemical Characterization of the Histidine Triad Protein PhtD as a Cell Surface Zinc-Binding Protein of Pneumococcus

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• 作者：Elodie Loisel ; Suneeta Chimalapati ; Catherine Bougault ; Anne Imberty ; Benoit Gallet ; Anne Marie Di Guilmi ; Jeremy Brown ; Thierry Vernet ; Claire Durmort
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：May 3, 2011
• 年：2011
• 卷：50
• 期：17
• 页码：3551-3558
• 全文大小：900K
• 年卷期：v.50,no.17(May 3, 2011)
• ISSN：1520-4995

文摘

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 Zn²⁺ concentrations within the various host niches. AdcAII was identified as a pneumococcal Zn²⁺-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 Zn²⁺ binds (K_d = 131 卤 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 Zn²⁺, that they interact directly in vitro, and that they are colocalized at the bacterial surface. These results suggest the common involvement of the AdcAII鈭扨htD system in pneumococcal zinc homeostasis.