Probing Interactions between the Curli Accessory Protein CsgE and Human Islet Amyloid Polypeptide

Abstract

Curli fibers are known to be involved in bacterial adhesion to surfaces, cell aggregation, and biofilm formation. Curli belong to a class of fibers known as amyloids. Curli assembly requires 5 proteins: CsgA, CsgB, CsgE, CsgF, and CsgG. CsgA and CsgB are the major structural components of curli. CsgG is an outer membrane protein responsible for the secretion of CsgA and CsgB to the extracellular surface. CsgE and CsgF are thought to be chaperon proteins which are responsible for the transport of CsgA and CsgB in the periplasm. It has been shown that CsgE inhibits the aggregation of CsgA, the main component of curli fibers. However, not much is known about the specific interactions between these two proteins. We employed a series of single cysteine mutants of CsgE and fluorescence quenching to investigate the interaction of CsgE with CsgA and with human islet amyloid polypeptide another amyloidogenic protein unrelated to curli formation.