Biology subjects

Tranter, D.

Publications and source records attributed to Tranter, D..

5 recordsLinked to original sources

bioRxiv2026

Solvent specific bioactivities of cone, leaf, and stem extracts from a native Finnish wild hop

The genetically authenticated Finnish hop genotype LUKE 2541 obtained from wild was evaluated for antibacterial, anti-inflammatory, and anticancer activities. Water extracts from hop cones inhibited the Gram-positive bacteria Staphylococcus aureus and Bacillus cereus, with MIC values of 0.094- 0.188mg/mL, whereas Gram-negative strains showed limited sensitivity. In LPS-primed THP-1 cells, both IPA and IPA-Control extracts reduced reactive oxygen species formation in a dose-dependent manner, exhibiting similar IC50 values (50.41{micro}g/mL and 35.41{micro}g/mL). This hop genotype also displayed clear tissue- and solvent-dependent antiproliferative effects in human cancer cell lines. Bioactivity was strongly enriched in hop cones and predominantly associated with non-polar extracts, particularly hexane and dichloromethane fractions, which produced marked, dose-dependent reductions in cell viability. In contrast, aqueous and methanolic extracts were largely inactive, underscoring the critical importance of extraction chemistry and tissue selection. Sensitivity varied among cancer cell lines, with colorectal cells generally more responsive and leukemia cells less affected, highlighting cell-specific susceptibility. Further research is needed to elucidate underlying mechanisms, determine selectivity toward non-malignant cells, and identify the active compounds responsible for all in all investigated effects.

biochemistry↗

bioRxiv2023

The Sec61/TRAP Translocon Scrambles Lipids

Cell growth relies on the rapid flip-flop of newly synthesized lipids across the ER membrane. This process is facilitated without the need for ATP by specific membrane proteins--scramblases--a few of which have been very recently identified in the ER. We have previously resolved the structure of the translocon-associated protein (TRAP) bound to the Sec61 translocon in the ER membrane, and found this complex to render the membrane locally thinner. Moreover, Sec61 and TRAP each contain a crevice rich in polar residues that can shield a lipid head group as it traverses the hydrophobic membrane environment. We thus hypothesized that both Sec61 and TRAP act as ER scramblases. Here, we characterized the scrambling activity of Sec61 and TRAP using extensive molecular dynamics simulations. We observed that both Sec61 and TRAP efficiently scramble lipids via a credit card mechanism. We analyzed the kinetics and thermodynamics of lipid scrambling and demonstrated that local membrane thinning provides a key contribution to scrambling efficiency. Both proteins appear seemingly selective towards phosphatidylcholine lipids over phosphatidylethanolamine and phosphatidylserine, yet this behavior rather reflects the trends observed for these lipids in a protein-free membrane. The identified scrambling pathway in Sec61 structure is physiologically rarely unoccupied due to its role in protein translocation. Furthermore, we found that the scrambling activity of this pathway might be impeded by the presence of ions at a physiological concentration. However, the trimeric bundle of TRAP{beta}, TRAP{gamma}, and TRAP{delta} might provide scrambling activity insensitive to the functional state of the translocon and the solvent conditions.

biophysics↗

bioRxiv2022

Molecular view of ER membrane remodeling by the Sec61/TRAP translocon

Protein translocation across the endoplasmic reticulum (ER) membrane is an essential initial step in protein entry into the secretory pathway. The conserved Sec61 protein translocon facilitates polypeptide translocation and coordinates cotranslational polypeptide processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation or cotranslational modifications such as N-glycosylation remains unknown. Here, we demonstrate the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by Cryo-EM. The interactions with ribosome anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its the lumenal leaflet. We propose a model for how TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen by direct polypeptide interactions.

biochemistry↗

bioRxiv2022

Signal peptide mimicry primes Sec61 for client-selective inhibition

Preventing the biogenesis of disease-relevant proteins is an attractive therapeutic strategy, but attempts to target essential protein biogenesis factors have been hampered by excessive toxicity. Here, we describe KZR-8445, a cyclic depsipeptide that targets the Sec61 translocon and selectively disrupts secretory and membrane protein biogenesis in a signal peptide-dependent manner. KZR-8445 potently inhibits the secretion of proinflammatory cytokines in primary immune cells and is highly efficacious in a mouse model of rheumatoid arthritis. A cryo-EM structure reveals that KZR-8445 occupies the fully opened Se61 lateral gate and blocks access to the lumenal plug domain. KZR-8445 binding stabilizes the lateral gate helices in a manner that traps select signal peptides in the Sec61 channel and prevents their movement into the lipid bilayer. Our results establish a framework for the structure-guided discovery of novel therapeutics that selectively modulate Sec61-mediated protein biogenesis.

biochemistry↗

bioRxiv2021

Snapshots of actin and tubulin folding inside the TRiC chaperonin

The integrity of a cells proteome depends on correct folding of polypeptides by chaperonins. The TCP-1 ring chaperonin (TRiC) acts as obligate folder for >10% of cytosolic proteins, including cytoskeletal proteins actin and tubulin. While its architecture and how it recognises folding substrates is emerging from structural studies, the subsequent fate of substrates inside the TRiC chamber is not defined. We trapped endogenous human TRiC with substrates (actin, tubulin) and co-chaperone (PhLP2A) at different folding stages, for structure determination by cryogenic electron microscopy. The already-folded regions of client proteins are anchored at the chamber wall, positioning unstructured regions towards the central space to achieve their folding. Substrates engage with different sections of the chamber during the folding cycle, coupled to TRiC open-and-close transitions. Furthermore, the cochaperone PhLP2A modulates folding, acting as a molecular strut between substrate and TRiC chamber. Our structural snapshots piece together an emerging atomistic model of client protein folding through TRiC.

biochemistry↗