# The Curli Accessory Protein CsgF of Salmonella Typhimurium Influences the in vitro Aggregation of Human Islet Amyloid Polypeptide

## TL;DR

A bacterial protein called CsgF from Salmonella prevents the clumping of a human amyloid protein in laboratory experiments.

## Contribution

This study reveals a novel role for CsgF in inhibiting human islet amyloid polypeptide aggregation.

## Key findings

- CsgF prevents hIAPP aggregation as shown by no increase in Thioflavin T fluorescence.
- The C-terminal half of CsgF is sufficient to inhibit hIAPP aggregation.
- The N-terminal 65 residues of CsgF are not required for this inhibitory effect.

## Abstract

The Curli secretion gene product F (CsgF) is a critical component of the assembly of Curli, proteinaceous filaments, found on the outer surface of gram-negative bacteria such as
E. Coli
and
Salmonella
. Herein we describe the ability of CsgF to influence the in-vitro aggregation of human islet amyloid polypeptide (hIAPP), an amyloidogenic polypeptide that is unrelated to Curli. In the presence of CsgF no increase in Thioflavin T fluorescence was observed for freshly solubilized hIAPP monitored as a function of time, suggesting that CsgF prevents the aggregation of hIAPP during the period of observation. A variant of CsgF lacking the first 65 residues in the N-terminus of CsgF retained the ability to inhibit the aggregation of hIAPP suggesting that the ability of CsgF to inhibit the aggregation of hIAPP is mediated by the C-terminal half of the protein.