TapA acts as specific chaperone in TasA filament formation by strand complementation

authored by

Yvette Roske, Florian Lindemann, Anne Diehl, Nils Cremer, Victoria A. Higman, Brigitte Schlegel, Martina Leidert, Kristina Driller, Kürşad Turgay, Peter Schmieder, Udo Heinemann, Hartmut Oschkinat

Abstract

Studying mechanisms of bacterial biofilm generation is of vital importance to understanding bacterial cell-cell communication, multicellular cohabitation principles, and the higher resilience of microorganisms in a biofilm against antibiotics. Biofilms of the nonpathogenic, gram-positive soil bacterium Bacillus subtilis serve as a model system with biotechnological potential toward plant protection. Its major extracellular matrix protein components are TasA and TapA. The nature of TasA filaments has been of debate, and several forms, amyloidic and non-Thioflavin T-stainable have been observed. Here, we present the three-dimensional structure of TapA and uncover the mechanism of TapA-supported growth of nonamyloidic TasA filaments. By analytical ultracentrifugation and NMR, we demonstrate TapA-dependent acceleration of filament formation from solutions of folded TasA. Solid-state NMR revealed intercalation of the N-terminal TasA peptide segment into subsequent protomers to form a filament composed of β-sandwich subunits. The secondary structure around the intercalated N-terminal strand β0 is conserved between filamentous TasA and the Fim and Pap proteins, which form bacterial type I pili, demonstrating such construction principles in a gram-positive organism. Analogous to the chaperones of the chaperone-usher pathway, the role of TapA is in donating its N terminus to serve for TasA folding into an Ig domain-similar filament structure by donor-strand complementation. According to NMR and since the V-set Ig fold of TapA is already complete, its participation within a filament beyond initiation is unlikely. Intriguingly, the most conserved residues in TasA-like proteins (camelysines) of Bacillaceae are located within the protomer interface.

Organisation(s)

Institute of Microbiology

External Organisation(s)

Max Delbrück Center for Molecular Medicine (MDC) in the Helmholtz Association
Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)
University of Leicester
Max Planck Unit for the Science of Pathogens (MPUSP)
Freie Universität Berlin (FU Berlin)

Type

Article

Journal

Proceedings of the National Academy of Sciences of the United States of America

Volume

120

Pages

e2217070120

ISSN

0027-8424

Publication date

25.04.2023

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General

Electronic version(s)

https://doi.org/10.1073/pnas.2217070120 (Access: Open)