Universität zu Köln

Wu, Yuang ORCID: 0000-0002-1689-151X (2022). Structural basis for the inhibition of a bacterial NLR and insights into its activation. PhD thesis, Universität zu Köln.

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Abstract

To cope with a constantly changing environment, living organisms acquire different signaling pathways in response to internal and external stimuli. The STAND (signal transduction ATPases with numerous domains) is a family of intracellular signaling proteins widely exist across kingdoms. In eukaryotes, STAND proteins have a key role in innate immunity and act as sensors for the detection of microbes, defects in STAND signaling are often found as the underlying cause of cancer and other human diseases. Bacterial STAND proteins mainly function as transcription regulators, which monitor the availability of nutrients and facilitate their efficient utilization. MalT is a transcription activator of the maltose operon in E .coli (Escherichia coli) and has all the hallmarks of STAND family proteins. MalT transcriptionally controls the activity of genes involved in maltose/maltodextrin uptake and catabolism, while its own activity is governed by inducer maltotriose and repressor proteins such as MalK, MalY, and Aes. MalT harbors a NOD (nucleotide-binding and oligomerization) module at the protein N-terminal (amino-terminal) end, followed by a SUPR-type sensor domain and a DNA-binding domain at the C-terminal (carboxyl terminal) end. In this study, the structure of an inhibitory complex containing MalT and MalY was solved by cryo-EM (cryo-electron microscopy), revealing the mechanisms of MalT inhibition and activation. Inhibition of MalT was shown to be mediated by inter- and intramolecular interactions. The very N-terminal region of MalT makes contacts with both NBD (nucleotide-binding domain) and WHD (wing-helix domain), keeping the NOD module closed. This resting state is further maintained by MalY, which interacts with MalT via one oligomerization surface on the NBD. Upon maltotriose binding, domain remodeling of MalT occurs and allosterically disengages the inhibitory contacts, exposing another oligomerization surface composed of structural elements from the N-terminal region, leading to nucleotide exchange and MalT activation. Ligand-binding together with oligomerization stabilizes the C-terminal domains of MalT for DNA-binding and transcription initiation at MalT-dependent promoters. The presented results suggest a common strategy for protein inhibition adopted by STAND members during the course of evolution and provide insights into transcription regulation by STAND proteins, demonstrating the functional versatility of this protein family with a relatively conserved domain architecture.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Wu, Yuang ywu@mpipz.mpg.de orcid.org/0000-0002-1689-151X UNSPECIFIED
URN:	urn:nbn:de:hbz:38-641690
Date:	22 November 2022
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Plant Breeding Research
Subjects:	Natural sciences and mathematics Life sciences
Uncontrolled Keywords:	Keywords Language STAND English maltose system UNSPECIFIED transcription UNSPECIFIED
Date of oral exam:	19 September 2022
Referee:	Name Academic Title Chai, Jijie Professor Parker, Jean Professor
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/64169