The
CsgA protein in Escherichia coli can
self-assemble into an amyloid nanofiber, making it a promising
biomaterial capable of resisting harsh environments. The assembling
and unfolding mechanism of a single CsgA molecule is essential for
all applications of CsgA materials but remains poorly understood.
CsgA-CBD and Mfp5-CsgA are chimeric proteins generated by introducing
the chitin-binding domain (CBD) and mussel foot protein 5 (Mfp5) into
CsgA. In this study, we used magnetic tweezers to study the mechanical
properties of a single CsgA molecule and the CsgA-CBD and Mfp5-CsgA
assembled nanofibers. Our results demonstrated that the unfolding
spectra of five β-sheets of a single CsgA molecule were not
uniform and that several β-sheets simultaneously broke after
an external force was applied. We applied ∼331 kcal/mol of
work, via mechanochemical coupling, to unfold CsgA to a 94.6% strain.
The average persistence lengths of the CsgA-CBD and Mfp5-CsgA nanofibers
were 2.7 and 4.5 nm, respectively, while Young’s moduli of
the two nanofibers were 42.8 and 56.1 MPa, respectively, both of which
were less than those of the CsgA nanofiber. A relatively high force
was required to unfold some of the nanofibers, which indicated that
mechanical stimuli could help remove amyloid particles. This study
assesses the mechanical properties of a single CsgA and lays the foundation
for its subsequent use as a biological material and provides new insights
into mechanochemical coupling nanofibers to design materials with
tunable functions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.