Biology subjects

Morton, C. J.

Publications and source records attributed to Morton, C. J..

4 recordsLinked to original sources

bioRxiv2024

A novel PGRL1 paralog refined the control of photoprotection in grasses and facilitated cell specialisation in C4 photosynthesis

The PGR5-PGRL1 pathway protects plants from photodamage by regulating electron flow to maintain Photosystem I in an oxidised state. Grasses possess two PGRL1 paralogs, but their functional roles have remained unknown. Here, we show that the ancestral PGRL1 paralog, PGRL1, which is conserved across algae and land plants, is enriched in the mesophyll cells of grasses that perform the NADP-ME subtype of C4 photosynthesis. In contrast, the grass-specific paralog PGRL1{beta} is enriched in bundle sheath cells. To investigate the functional significance of this cell-specific expression, we generated gene-edited lines of the NADP-ME C4 grass Setaria viridis lacking either PGRL1 paralog. We found that PGRL1{beta} in bundle sheath cells was required for rapid photoprotection, enabling Photosystem I oxidation five seconds faster during transitions from darkness to high light. In contrast, PGRL1 in mesophyll cells was essential for maintaining Photosystem I oxidation under steady-state high-light conditions. We propose that these complementary functions arise from structural differences within the lumen-facing regions of the two paralogs, providing a mechanistic basis for their distinct roles in regulating photoprotection. The conservation of this dual PGRL1 system across grasses suggests that functional specialisation of the paralogs expands the dynamic range of protective responses, enhancing photosynthetic performance under fluctuating and high-light stress conditions.

plant biology↗

bioRxiv2024

A potent and selective reaction hijacking inhibitor of Plasmodium falciparum tyrosine tRNA synthetase exhibits single dose oral efficacy in vivo

The Plasmodium falciparum cytoplasmic tyrosine tRNA synthetase (PfTyrRS) is an attractive drug target that is susceptible to reaction-hijacking by AMP-mimicking nucleoside sulfamates. We previously identified an exemplar pyrazolopyrimidine ribose sulfamate, ML901, as a potent pro-inhibitor of PfTyrRS. Here we examined the stage specificity of action of ML901, showing very good activity against the schizont stage, but lower trophozoite stage activity. We explored a series of ML901 analogues and identified ML471, which exhibits improved potency against trophozoites and enhanced selectivity against a human cell line. Additionally, it has no inhibitory activity against human ubiquitin-activating enzyme (UAE) in vitro. ML471 exhibits low nanomolar activity against asexual blood stage P. falciparum and potent activity against liver stage parasites, gametocytes and transmissible gametes. It is fast-acting and exhibits a long in vivo half-life. ML471 is well-tolerated and shows single dose oral efficacy in the SCID mouse model of P. falciparum malaria. We confirm that ML471 is a pro-inhibitor that is converted into a tight binding Tyr-ML471 conjugate by the PfTyrRS enzyme. A crystal structure of the PfTyrRS/ Tyr-ML471 complex offers insights into improved potency, while molecular docking into UAE provides a rationale for improved selectivity.

biochemistry↗

bioRxiv2022

Structures of the interleukin 11 signalling complex reveal dynamics of gp130 extracellular domains and the inhibitory mechanism of a cytokine variant

Interleukin (IL-)11, an IL-6 family cytokine, has pivotal roles in numerous autoimmune diseases, fibrotic complications, and solid cancers. Despite intense therapeutic targeting efforts, structural understanding of IL-11 signalling and mechanistic insights into current inhibitors is lacking. Here we present cryo-EM and crystal structures of the IL-11 signalling complex, including the complex containing the complete extracellular domains of the shared IL-6 family {beta}-receptor, gp130. We show that the membrane-proximal domains of gp130 are dynamic and do not participate in complex assembly. We demonstrate that the cytokine mutant IL-11 Mutein competitively inhibits signalling in human cell lines. Structural shifts in IL-11 Mutein underlie inhibitory activity by altering cytokine binding interactions at all three receptor-engaging sites and abrogating the final gp130 binding step. Our results reveal the structural basis of IL-11 signalling, define the molecular mechanisms of an inhibitor, and advance understanding of gp130-containing receptor complexes, with potential applications in therapeutic development.

cell biology↗

bioRxiv2020

Mutations in an intracellular vestibule that bifurcates from the pore of ClC-1 chloride ion channels affect anion permeation

The ubiquitous CLC protein superfamily consists of channels, that permit passive diffusion of Cl ions across biological membranes, and pumps, that can actively transport Cl ions against their electrochemical gradient; yet, puzzlingly, both types share a strongly conserved Cl ion transport pathway comprised of three consecutive binding sites. This raises the question; how does the same pathway support passive diffusion in CLC channels and active transport in CLC pumps? Based on high-resolution structural data current theories suggest that subtle structural differences in the conserved pathway allow CLC channels to leak Cl ions. A recent cryo-electron microscopy structure of the human ClC-1 channel does not show occupancy of the central Cl ion binding site but reveals a wide intracellular vestibule that bifurcates from the conserved pathway in this region. Here we show that replacing residues that line the ClC-1 intracellular vestibule with the corresponding residues of CLC pumps resulted in interactions between permeating anions at neighbouring binding sites and altered anion selectivity. Removing the side chain of a strictly conserved tyrosine residue, that coordinates Cl ion at the central binding site of CLC pumps, removed multi-ion behaviour in ClC-1 mutants. In contrast, removing the side chain of a highly conserved glutamate residue that transiently occupies Cl ion binding sites, as part of the transport mechanism of CLC pumps and the mechanism that opens and closes CLC channels, only partially removed multi-ion behaviour in ClC-1 mutants. Our findings show that structural differences between CLC channels and pumps, outside of the conserved Cl ion transport pathway, fundamentally affect anion permeation in ClC-1 channels. SummarySome CLC proteins are passive Cl- channels while others are active Cl- pumps but, paradoxically, both share a conserved, canonical, Cl- permeation pathway. Here Bennetts, Morton and Parker show that pump-like mutations in a poorly conserved region, located remotely from the canonical pathway, affect anion permeation in human ClC-1 channels.

biochemistry↗