Chromosome-level genome assembly of the Hong Kong Krabby Harvestman (Heterobiantes geniculatus) (Opiliones: Epedanidae)

Posted by
  Chromosome-level genome assembly of the Hong Kong Krabby Harvestman (Heterobiantes geniculatus) (Opiliones: Epedanidae) Abstract Harvestmen (order Opiliones) are a diverse order within Arachnida that are widely distributed across the globe, and are known for their ecological roles as detritivores and predators in terrestrial ecosystems. However, the scarcity of high-quality genomic resources, especially for Asian endemic lineages, has hindered research into their morphological adaptations and evolutionary history. Here, we generated a chromosome-level genome assembly for the Hong Kong Krabby Harvestman ( Heterobiantes geniculatus ), a species endemic to Asia belonging to the family Epedanidae (Opiliones: Laniatores), by integrating PacBio HiFi long reads, Illumina short reads, RNA-seq, and Hi-C chromatin conformation capture technologies. The final genome assembly spans 3.15 Gb, with a scaffold N50 of 101.15 Mb, and a contig N50 of 8.10 Mb. Notably, 82.91% of the assembly was anc...

Molecular mechanism of α-latrotoxin action

Posted by

 

Molecular mechanism of α-latrotoxin action

Abstract


The potent neurotoxic venom of the black widow spider contains a cocktail of seven phylum-specific latrotoxins (LTXs), but only one, α-LTX, targets vertebrates. This 130 kDa toxin binds to receptors at presynaptic nerve terminals and triggers a massive release of neurotransmitters. It is widely accepted that LTXs tetramerize and insert into the presynaptic membrane, thereby forming Ca2+-conductive pores, but the underlying mechanism remains poorly understood. LTXs are homologous and consist of an N-terminal region with three distinct domains, along with a C-terminal domain containing up to 22 consecutive ankyrin repeats. Here we report the first high resolution structures of the vertebrate-specific α-LTX tetramer in its prepore and pore state. Our structures, in combination with AlphaFold2-based structural modeling and molecular dynamics simulations, reveal dramatic conformational changes in the N-terminal region of the complex. Four distinct helical bundles synchronously rearrange to progressively form a highly stable 15 nm cation-impermeable coiled-coil stalk. This stalk, in turn, positions an N-terminal pair of helices within the membrane, thereby enabling the assembly of a cation-permeable channel. Taken together, these data unveil a unique mechanism for membrane insertion and channel formation, characteristic of the LTX family, and provide the necessary framework for advancing novel therapeutics and biotechnological applications.


Molecular mechanism of α-latrotoxin action Bjoern Udo Klink, Azadeh Alavizargar, Kalyankumar Karthik Subramaniam, Minghao Chen, Andreas Heuer, Christos Gatsogiannis
bioRxiv 2024.03.06.583760; doi: https://doi.org/10.1101/2024.03.06.583760