Optical Monitoring of In Situ Iron Loading into Single, Native Ferritin Proteins

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Ferritin is crucial for iron storage and release in organisms, preventing iron dysregulation diseases.
• The transition between apo-ferritin (empty) and holo-ferritin (iron-loaded) is key for iron homeostasis.
• Previous studies relied on ensemble measurements or modified single-molecule techniques.

Purpose of the Study:

• To investigate the real-time dynamics of iron ion loading and biomineralization within individual, unlabeled ferritin proteins.
• To establish a novel method for observing ferritin's iron uptake mechanism at the single-molecule level.

Main Methods:

• Utilized optical nanotweezers to trap single apo-ferritin and holo-ferritin molecules indefinitely.
• Monitored the structural dynamics and iron loading/unloading processes of individual ferritin proteins in real time.

Main Results:

• Successfully trapped and distinguished single, unlabeled apo- and holo-ferritins.
• Observed and quantified the real-time dynamics of iron ion incorporation and release within single ferritin proteins.
• Provided unprecedented visualization of ferritin biomineralization at the single-molecule level.

Conclusions:

• This work presents the first real-time single-molecule study of ferritin iron dynamics without protein labeling.
• Deepens the understanding of ferritin's iron uptake mechanism and biomineralization processes.
• May pave the way for developing novel therapeutics targeting iron-related disorders.