# Analysis of Amyloid Fibrillation of Two Family 1 Glycoside Hydrolases

## TL;DR

This paper studies how two similar enzymes form amyloid fibers under various pH and temperature conditions.

## Contribution

The study reveals that amyloid fibrillation is a common phenomenon in glycoside hydrolases due to protein misfolding.

## Key findings

- Both BglA and BglB form amyloid fibers under acidic and alkaline pH and specific temperature ranges.
- Circular dichroism confirmed a structural transition from α-helix to β-sheet during fibrillation.
- Fibrillation is driven by protein misfolding under conditions that disrupt native conformation.

## Abstract

The formation and analysis of amyloid fibers by two β-glucosidases, BglA and BglB, belonging to the GH1 enzyme family, are reported. Both proteins have the (β/α)8 TIM-barrel fold, which is characteristic of this family and is also the most common protein structure. BglA is an octamer, whereas BglB is a monomer. Amyloid fibrillation using pH and temperature as perturbing agents was investigated using fluorescence spectroscopy as a preliminary approach and corroborated using wide-field optical microscopy, confocal microscopy, and field-emission scanning electron microscopy. These analyses showed that both enzymes fibrillate at a wide range of acidic and alkaline conditions and at several temperature conditions, particularly at acidic pH (3–4) and at temperatures between 45 and 65 °C. Circular dichroism spectroscopy corroborated the transition from an α-helix to a β-sheet secondary structure of both proteins in conditions where fibrillation was observed. Overall, our results suggest that fibrillation is a rather common phenomenon caused by protein misfolding, driven by a transition from an α-helix to a β-sheet secondary structure, that many proteins can undergo if subjected to conditions that disturb their native conformation.