Protein quality control and antibiotics

the role of the small heat shock protein YocM and the disaggregase ClpC in B. subtilis

authored by

Ingo Hantke

supervised by

Kürşad Turgay

Abstract

All living cells have to deal with fluctuations of abiotic factors, such as temperature and salt content, which can cause different types of proteotoxic stress. A functional proteome depends on an intricate protein quality control network (PQC) of chaperones and proteases, which is highly conserved in all domains of life. As one part of the PQC system, small heat shock proteins (sHsp) protect proteins from unfolding and facilitate refolding in cooperation with molecular chaperons. During this work, YocM was identified as the first stress-related sHsp of B. subtilis, ensuring survival of cells during salt shock. Furthermore, a YocM-mCherry fusion protein was established as a protein aggregate marker. Thereby, McsB was identified as the main adaptor protein for disaggregation of subcellular protein aggregates by the Hsp100/Clp protein ClpC during heat stress, which was dependent on its protein arginine kinase activity. In general, protein disaggregation instead of degradation was observed to be the predominant process regarding protein aggregate removal in stress response in B. subtilis. ClpC as a central player of PQC and stress response was recently identified as a target for various antibiotic compounds (e.g. cyclomarin). During this work it was demonstrated that a clpC F436A mutation led to severe formation of protein aggregates in vivo and substantially impaired survival of B subtilis, which was dependent on the presence of McsB. As this deregulation of ClpC by exchange of only one amino acid residue displayed such a toxic phenotype, ClpC was confirmed to be an adequate target for antibiotics. Consequently, a ClpC-target based screen was successfully established and validated in B. subtilis as proof of concept to discover and characterize novel antibiotics compounds that address the PQC system in Gram-positive pathogenic bacteria.

Organisation(s)

Institute of Microbiology

Type

Doctoral thesis

No. of pages

194

Publication date

2019

Publication status

Published

Electronic version(s)

https://doi.org/10.15488/5491 (Access: Open)