Electronic Circular Dichroism Detects Conformational Changes Associated with Proteasome Gating Confirmed Using AFM...

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• Proteasome dysregulation is linked to chronic diseases like cancer.
• Proteasome gating controls cellular proteostasis and is crucial for drug design.
• Understanding gate conformations is key for developing targeted therapies.

Purpose of the Study:

• To explore electronic circular dichroism (ECD) for monitoring proteasome gate conformations.
• To validate ECD as a tool for detecting structural changes associated with proteasome gating.
• To assess ECD's utility in characterizing ligand-induced proteasome gate status.

Main Methods:

• Utilized UV-region ECD spectroscopy to analyze wild-type yeast and human 20S proteasomes.
• Compared ECD spectra of closed and open-gate proteasome mutants.
• Applied ECD to monitor conformational changes induced by SDS and a tetracationic porphyrin (H2T4).
• Corroborated ECD findings with Atomic Force Microscopy (AFM) imaging of the proteasome alpha ring.

Main Results:

• ECD spectra showed distinct changes at 220 nm correlating with proteasome gate status (open vs. closed).
• Increased ECD intensity at 220 nm indicated higher random coil and beta-turn structures, associated with gate opening.
• H2T4 treatment induced a significant increase in the 220 nm ECD band, signifying induced gate opening.
• AFM results confirmed the ECD data, showing a decrease in closed-gate conformations upon H2T4 treatment.

Conclusions:

• ECD spectroscopy is a viable and convenient method for monitoring proteasome conformational changes related to gating.
• The correlation between ECD and structural data supports its application in drug design.
• This approach facilitates the characterization of exogenous proteasome regulators.