Structural characterisation of the HT3 motif of the polyhistidine triad protein D from Streptococcus pneumoniae

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• * Streptococcus pneumoniae (pneumococcus) is a significant human pathogen requiring zinc ions (Zn²⁺) for survival and virulence.
• * Polyhistidine triad protein D (PhtD) is implicated in pneumococcal Zn²⁺ homeostasis, but its function lacks detailed mechanistic and structural understanding.

Purpose of the Study:

• * To elucidate the structural basis of PhtD's role in Zn²⁺ homeostasis in Streptococcus pneumoniae.
• * To provide insights into the mechanism of Zn²⁺ binding by PhtD.

Main Methods:

• * Determination of the crystal structure of the PhtD^269-339 fragment, which contains the third Zn²⁺-binding histidine triad (HT) motif.
• * Structural analysis to understand Zn²⁺ binding interactions.

Main Results:

• * The crystal structure of PhtD^269-339 was determined, revealing details of the third HT motif.
• * Analysis indicates Zn²⁺ binding occurs at the protein surface.
• * All five HT motifs within the protein are predicted to bind Zn²⁺ and exhibit similar structural features.

Conclusions:

• * The determined structure provides crucial insights into how PhtD binds Zn²⁺.
• * This structural information advances the understanding of Zn²⁺ acquisition mechanisms mediated by Pht proteins in pneumococcus.
• * Findings contribute to understanding pneumococcal pathogenesis and potential therapeutic targets.