Structural basis for human RegⅢα filament formation.

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Regenerating III alpha (RegIIIα) is a key antibacterial protein in the digestive tract.
• RegIIIα functions by forming pores on bacterial membranes, leading to cell lysis.
• Previous models suggested RegIIIα hexamers assemble into filaments, reducing activity, but high-resolution structures were lacking.

Purpose of the Study:

• To determine the high-resolution cryo-electron microscopy (cryo-EM) structure of RegIIIα filaments.
• To elucidate the molecular mechanisms of RegIIIα assembly and function.
• To understand the inhibitory role of the RegIIIα pro-segment.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine filament structure at 2.2 Å resolution.
• Structural analysis of RegIIIα filaments.
• Biochemical assays to investigate assembly interfaces and lipid interactions.

Main Results:

• The first near-atomic structure of RegIIIα filaments was determined.
• Distinct subunit orientation compared to previous low-resolution models was observed.
• Two essential assembly interfaces were identified, with potential roles for lipids and the pro-segment in regulation.

Conclusions:

• The study provides critical structural insights into RegIIIα filament formation.
• Understanding RegIIIα assembly mechanisms is crucial for its physiological function and regulation.
• This work advances the understanding of C-type lectin-containing protein filament structures.