Structural Insights into Iron Ions Accumulation in Dps Nanocage

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• DNA-binding protein from starved cells (Dps) forms protective intracellular assemblies for bacterial DNA under stress.
• Dps functions as a ferritin-like protein, oxidizing ferrous ions (Fe2+) and storing ferric ions (Fe3+) in its nanocage.
• This iron storage provides bacteria with physical and chemical protection.

Purpose of the Study:

• To investigate the effect of Fe2+ concentration and incubation time on iron mineral formation within the Dps nanocage from Escherichia coli using cryo-electron microscopy.
• To characterize the morphology and composition of iron clusters formed inside Dps nanocages.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to visualize iron ion accumulation in Dps nanocages.
• Experiments involved varying Fe2+ concentrations and incubation times during the formation of iron minerals.

Main Results:

• Fe2+ concentration and incubation time had minimal impact on the overall volume and morphology of iron minerals within Dps nanocages.
• Increased Fe2+ levels resulted in a higher proportion of larger iron mineral clusters.
• These larger clusters were found to be composed of discrete subunits, approximately 1-1.5 nm in size.

Conclusions:

• The formation of iron minerals within Dps nanocages is robust and not significantly affected by moderate changes in Fe2+ concentration or incubation duration.
• While the overall structure is consistent, higher Fe2+ availability influences the aggregation into larger, subunit-based clusters within the Dps nanocage.