Insights into the distribution and ecology of the funnelweb spider Macrothele calpeiana in Portugal

Posted by
  Insights into the distribution and ecology of the funnelweb spider Macrothele calpeiana in Portugal Abstract Biodiversity surveys are critical to prevent decline and extinction of ill-/unknown species through timely conservation action. This is particularly relevant when the species are neither iconic nor flagships, therefore lessening the potential for accessing conservation means, such as in the case of the mygalomorph spider Macrothele calpeiana. The species is endemic to southern Iberia but its distribution and ecology is barely documented in Portugal. Therefore, we made a comprehensive survey throughout its estimated range in the south of the country. The species is spread unevenly and patchily throughout low mountainous terrain in south/southwest Portugal, preferably along shale/ greywacke/clay roadside banks. It seems rare in the surrounding limestone area to the south and absent from the peneplain to the north. The webs were found in groups averaging 10.0±15.2 webs/site a...

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