Biology subjects

Wiseman, B.

Publications and source records attributed to Wiseman, B..

6 recordsLinked to original sources

bioRxiv2026

Assembly and activation of the AAA+ motor of the multi-subunit cobaltochelatase

Cobalamin is a complex yet essential cobalt-containing cofactor synthesized exclusively by prokaryotes and archaea. Aerobic cobalamin biosynthesis requires the CobNST multi-subunit class I cobaltochelatase for cobalt incorporation. Cobalt chelation is dependent on the energy transfer from the CobST AAA+/VWA motor unit to the substrate-binding catalytic unit (CobN). However, the mechanism for assembly and function of CobNST cobaltochelatase remains poorly understood. Here, we used cryo-EM to solve the structures of the AAA+ motor CobS, in the absence and presence of ATP and its VWA-partner protein CobT. Our data reveal that the AAA+ CobS assembles into various conformations, including hexameric planar rings and different spiral left-handed assemblies: hexamers, double rings and filaments. In the absence of nucleotide, the CobT N-terminal domain interacts with CobS left-handed oligomers, remaining in a half-assembled, nonfunctional motor unit. In the CobST complex, ATP induces conformational rearrangement of CobS from left-handed helical oligomers to a right-handed closed hexamer. The simultaneous repositioning of the CobT VWA domain to the AAA+ central pore shifts the motor unit to a functional state, ready-to-drive CobN-catalyzed chelation reaction. These findings define the mechanism for assembly and activation of the class I cobaltochelatase CobST motor.

biochemistry↗

bioRxiv2025

Intercellular mitochondrial transfer and transmitophagy in response to protein import dysfunction

Mitochondrial protein import is critical for organelle biogenesis and maintenance, essential processes for cellular homeostasis. Import dysfunction compromises cellular energy supplies which is damaging to cells, particularly those with high energetic demands like neurons. Previously, we have shown that import failure is rescued by intercellular mitochondrial transfer via tunnelling nanotubes (TNTs) however, the fate of the transferred mitochondria and the mechanistic basis for rescue was unresolved. Here, we show that bi-directional mitochondrial trafficking between cells harbouring import-defective and import-competent mitochondria has distinct regulation and consequences. Transferred import-defective mitochondria are highly fragmented and destined for canonical lysosomal degradation. In contrast, ROS-producing mitochondria at the periphery of cells with import-competent mitochondria are transferred into neighbouring cells undergoing import failure; these new arrivals then accumulate within previously uncharacterised mitochondrial degradation bodies (MBDs). We speculate that the co-operation of these distinct examples of TNT- mediated conventional and non-canonical transmitophagy instigate mitochondrial regeneration, and thereby rescue.

cell biology↗

bioRxiv2025

CryoEM of ATP-driven dynamics and itraconazole binding in a fungal ABC pump

Azole resistance in Candida species is often caused by the overexpression of Cdr1. Despite its clinical relevance, the structural basis for its ATP-driven efflux pump function remains elusive. We present four high-resolution cryo-EM structures for Candida glabrata Cdr1 under active turnover conditions in the absence and presence of ATP-Mg{superscript 2}, itraconazole, and vanadate. Additional transient cryo-EM structures were unveiled by 3D variability analysis offering a detailed view of the step-by-step transitions triggered by ATP-hydrolysis. The motion cascade starts with a 4 [A] piston-like retraction of the C-helix from the {gamma}-phosphate/vanadate of the hydrolyzed ATP. This causes the nearby transmembrane helix-1 (TMH-1) to open the drug-binding site via lateral displacement and unwinding of the inner-leaflet region of TMH-2. A reverse squeeze-and-push motion of TMH-2 possibly drives substrate extrusion. High resolution structures also reveal how itraconazole adapts its shape to fit into the drug-binding site. Our findings provide a dynamic structural framework for Cdr1-mediated azole resistance and the conserved chemo-mechanical cycle of ABC proteins, including non-membranous members.

biochemistry↗

bioRxiv2023

Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy

Post-fertilization cleavage of glycoprotein ZP2, a major subunit of egg zona pellucida (ZP) filaments, is crucial for mammalian reproduction by irreversibly blocking polyspermy. ZP2 processing is thought to inactivate a sperm-binding activity located upstream of the proteins cleavage site; however, its molecular consequences and connection with ZP hardening are unknown. Here we report X-ray crystallographic, cryo-EM and biochemical studies showing that cleavage of ZP2 triggers its oligomerization. Deletion of the ZP-N1 domain that precedes the cleavage site of mouse ZP2 allows it to homodimerize even without processing, and animals homozygous for this variant are subfertile by having a semi-hardened ZP that allows sperm attachment but hinders penetration. Combined with the structure of a native egg coat filament, which reveals the molecular basis of heteromeric ZP subunit interaction, this suggests that oligomerization of cleaved ZP2 cross-links the ZP, rigidifying it and making it physically impenetrable to sperm.

biophysics↗

bioRxiv2021

Drug-bound and -free outward-facing structures of a multidrug ABC exporter point to a swing mechanism

Multidrug ABC transporters translocate drugs across membranes by a mechanism for which the molecular features of drug release are so far unknown. Here, we resolved two ATP-Mg2+-bound outward-facing (OF) conformations of the Bacillus subtilis (homodimeric) BmrA, one by X-ray crystallography without drug, and another by single-particle cryo-EM with rhodamine 6G (R6G). Two R6G molecules bind to the drug-binding cavity at the level of the outer leaflet, between transmembrane (TM) helices 1-2 of one monomer and TM5-6 of the other. R6G induces a rearrangement of TM1-2, highlighting a flexibility that was confirmed by H/D exchange and molecular dynamics simulations. The latter also shows a fast post-release occlusion of the cavity driven by hydrophobicity. Altogether, these data support a new swing mechanism for drug transport.

biochemistry↗

bioRxiv2018

Conformational changes in Apolipoprotein N-acyltransferase (Lnt)

In bacteria, lipoproteins are important components of the cell envelope and are responsible for many essential cellular functions. They are produced by the post-translational covalent attachment of lipids that occurs via a sequential 3-step process controlled by three essential integral membrane enzymes. The last step of this process, unique to Gram negative bacteria, is the N-acylation of the terminal cysteine by Apolipoprotein N-acyltransferase (Lnt) to form the final mature lipoprotein. Here we report 2 crystal forms of this enzyme. In one form the enzyme crystallized with two molecules in the asymmetric unit. In one of those molecules the thioester acyl-intermediate is observed. In the other molecule, the crystal packing suggests one potential mode of apolipoprotein docking to Lnt. In the second crystal form the enzyme crystallized with one molecule in the asymmetric unit in an apparent apo-state remarkably devoid of any bound molecules in the large open substrate entry portal. Taken together, these structures suggest that the movement of the essential W237 is triggered by substrate binding and could help direct and stabilize the interaction between Lnt and the incoming substrate apolipoprotein.\n\nGraphical Abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC=\"FIGDIR/small/497412v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (55K):\norg.highwire.dtl.DTLVardef@318596org.highwire.dtl.DTLVardef@139463corg.highwire.dtl.DTLVardef@13213ecorg.highwire.dtl.DTLVardef@ba011b_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗