Understanding Curli Amyloid-Protein Aggregation by Hydrogen-Deuterium Exchange and Mass Spectrometry.

•Amyloid formation of CsgA protein in curli followed by pulsed HDX and MS.•Amyloid formation of CsgA also characterized by MS quantification of soluble protein.•One highly structured and one disordered species coexist during aggregation of CsgA.•Regions of CsgA that determine aggregation identifiable by HDX and MS.•Protein species involved in various stages of aggregation seen by TEM.