Structural Characterization of Fibrillar Aggregates of Proteins by Mass Spectrometry

Abstract

Fibrillar aggregates observed in vivo and in vitro are part of “abnormal” structures of proteins. Since many proteins are capable of forming such fibrillar aggregates that share characteristics of the cross-β structure at an atomic level, we consider the fibril structure as one of general states of proteins. It is thus profoundly important to reveal the fibril structure and mechanism of its formation. To this end, mass spectrometry is used as an essential tool by making full use of the inherent sensitivity and high information content. Especially, combination of proteolysis and mass spectrometry is a powerful technique to characterize structural features of the aggregated state of proteins. By identifying fragments produced in the course of proteolysis, it is possible to discern differences in local stability within the analyzed protein and to reconstruct the structure of the mature fibril. In this review, we explain several useful methods to characterize fibrillar aggregates by the combined use of proteolysis and mass spectrometry.