Biology subjects

Nanson, J. D.

Publications and source records attributed to Nanson, J. D..

3 recordsLinked to original sources

bioRxiv2026

Structural basis of canonical TIR-NLR activation in plant innate immunity

In plants, intracellular NLRs (nucleotide-binding leucine-rich repeat receptors) detect pathogen effector proteins, form oligomeric resistosomes, and activate ETI (effector-triggered immunity). NLRs contain N-terminal signaling, central NB-ARC (nucleotide-binding) and C-terminal LRR (leucine-rich repeat) domains. NLRs with N-terminal TIR (Toll/interleukin-1 receptor) domains (TNLs) hydrolyze NAD+ (nicotinamide adenine dinucleotide) to generate signaling molecules. We determined cryo-EM structures of flax M, a canonical non C-JID (C-terminal jellyroll/Ig-like domain) TNL, in both monomeric autoinhibited conformation, and tetrameric resistosome after activation by its rust fungal effector AvrM-A. AvrM-A homodimers dissociate into monomers to bind directly to the LRR and NB-ARC domains in the M resistosome. The resistosome structure includes a non-hydrolyzable NAD+ analogue, revealing the substrate NAD+ recognition mechanism by the TIR domains. M cleaves NAD+ and generates the same signaling compounds as the related flax TNL, L6. Our findings explain the mechanism of TNL signaling, and provide a basis for rational engineering of disease-resistant crops.

plant biology↗

bioRxiv2022

Chemical structures of cyclic ADP ribose (cADPR) isomers and the molecular basis of their production and signaling

Cyclic ADP ribose (cADPR) isomers are important signaling molecules produced by bacterial and plant Toll/interleukin-1 receptor (TIR) domains via NAD+ hydrolysis, yet their chemical structures are unknown. We show that v-cADPR (2cADPR) and v2-cADPR (3cADPR) isomers are cyclized by O-glycosidic bond formation between the ribose moieties in ADPR. Structures of v-cADPR (2cADPR)-producing TIR domains reveal that conformational changes are required for the formation of the active assembly that resembles those of Toll-like receptor adaptor TIR domains, and mutagenesis data demonstrate that a conserved tryptophan is essential for cyclization. We show that v2-cADPR (3cADPR) is a potent activator of ThsA effector proteins from Thoeris anti-phage defence systems and is responsible for suppression of plant immunity by the effector HopAM1. Collectively, our results define new enzymatic activities of TIR domains, reveal the molecular basis of cADPR isomer production, and establish v2-cADPR (3cADPR) as an antiviral signaling molecule and an effector-mediated signaling molecule for plant immunity suppression. One-Sentence SummaryThe chemical structures of two O-glycosidic bond-containing cyclic ADP ribose isomers, the molecular basis of their production, and their function in antiviral and plant immunity suppression by bacteria are reported.

biochemistry↗

bioRxiv2021

Crystal structure determination of the armadillo repeat domain of Drosophila SARM1 using MIRAS phasing

We describe the crystal structure determination of the ARM domain of Drosophila SARM1 (dSARM1ARM), which required combination of a number of sources of phase information in order to obtain interpretable electron density maps. SARM1 is a central executioner of the process of axon degeneration, a common feature of the early phase of a range of neurodegenerative diseases. SARM1 is held in the inactive state in healthy axons by its N-terminal auto-inhibitory ARM domain, and is activated to cleave NAD+ upon injury, triggering the subsequent axon degeneration. To characterize the molecular mechanism of SARM1 activation, we sought to determine the crystal structure of the SARM1 ARM domain. Here we describe the recombinant production and crystallization of dSARM1ARM, as well as unconventional process used for structure determination. Crystals were obtained in the presence of NMN, a precursor of NAD+ and a potential activator of SARM1, only after in situ proteolysis of the N-terminal 63 residues. After molecular replacement attempts failed, we determined the crystal structure of dSARM1ARM at 1.65 [A] resolution using the MIRAS phasing technique with the program autoSHARP, combining data from the native, SeMet-labelled, and Br-soaked crystals. The structure will further our understanding of the regulation of SARM1.

biophysics↗