Bacterial amphiphiles as amyloid inducers: Effect of Rhamnolipid and Lipopolysaccharide on FapC fibrillation

Publication date: Available online 14 August 2019Source: Biochimica et Biophysica Acta (BBA) - Proteins and ProteomicsAuthor(s): Zahra Najarzadeh, Jannik Nedergaard Pedersen, Gunna Christiansen, Seyed Abbas Shojaosadati, Jan Skov Pedersen, Daniel E. OtzenAbstractPseudomonas species export the amyloid-forming protein FapC to strengthen bacterial biofilm. P. species also produce the biosurfactant rhamnolipid (Rhl) and its outer membrane contains lipopolysaccharide (LPS). Given the possible contacts between FapC, Rhl and LPS, we here investigate how Rhl and LPS affect FapC fibrillation compared with SDS, known to promote fibrillation of proteins at sub-micellar concentrations. Micelles of all three surfactants help FapC bypass the nucleation lag phase, leading to rapid fibrillation, which persists even at high concentrations of micelles and incorporates almost all available FapC monomers. Fibrils formed at high micellar concentrations of Rhl and SDS seed fibrillation at low surfactant concentrations while retaining the original fibril structure. FapC interacts strongly with SDS to form a dense network of narrow fibrils. Small angle X-ray scattering (SAXS) analyses reveal that surfactants reduce the population of intermediates in the fibrillation process and detect a fast aggregation step over the first 2–4 h which precedes the main fibrillation monitored by Thioflavin T. An additional SAXS-detected rearrangement of early aggregates occurs after 4–10 h. At high Rhl concen...

Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - August 15, 2019 Category: Biochemistry Source Type: research