High-resolution analysis of the conformational transition of pro-apoptotic Bak at the lipid membrane.

Permeabilization of the outer mitochondrial membrane by pore-forming Bcl2 proteins is a crucial step for the induction of apoptosis. Despite a large set of data suggesting global conformational changes within pro-apoptotic Bak during pore formation, high-resolution structural details in a membrane environment remain sparse. Here, we used NMR and HDX-MS (Hydrogen deuterium exchange mass spectrometry) in lipid nanodiscs to gain important high-resolution structural insights into the conformational changes of Bak at the membrane that are dependent on a direct activation by BH3-only proteins. Furthermore, we determined the first high-resolution structure of the Bak transmembrane helix. Upon activation, α-helix 1 in the soluble domain of Bak dissociates from the protein and adopts an unfolded and dynamic potentially membrane-bound state. In line with this finding, comparative protein folding experiments with Bak and anti-apoptotic BclxL suggest that α-helix 1 in Bak is a metastable structural element contributing to its pro-apoptotic features. Consequently, mutagenesis experiments aimed at stabilizing α-helix 1 yielded Bak variants with delayed pore-forming activity. These insights will contribute to a better mechanistic understanding of Bak-mediated membrane permeabilization.

Updated Methods for the Production of Toxorhynchites rutilus septentrionalis (Diptera, Culicidae) for Use as Biocontrol Agent Against Container Breeding Pest Mosquitoes in Harris County, Texas.

The complex biologies of pestiferous mosquito species complicate the development of a single, across the board effective control measure. The use of traditional biological control through predators, parasitoids, and microbes, though part of a multimodal, integrated pest management approach, is scant in current standard mosquito control operations. At this time, traditional, whole organism mosquito biocontrol agents are not commercially available, and if their integration into a release program is desired, they must be developed in-house. The aim of our program was to incorporate releasing natural enemies to disrupt and suppress the target pest mosquito's population by matching the agent with the target's biology, before or concurrent to pesticide use. A current focus is suppressing peridomestic, container breeders of high medical significance, such as Aedes aegypti (Linnaeus), (Diptera, Culicidae) and Aedes albopictus (Skuse) (Diptera, Culicidae), through larval reduction with augmentative releases of laboratory-reared, native mosquito assassins Toxorhynchites rutilus septentrionalis (Dyar & Knab). When raised in communal settings, Tx. rutilus' aggressive feeding behavior and cannibalistic tendencies require an extreme loss tolerance in adult production rates. In addition, offering prey mosquitoes exclusively as Tx. rutilus' juvenile food extends larval development by multiple days. While this may be desirous in the wild, it proves inefficient during production. Here, we provide an individual rearing method as well as an alternative diet protocol, which maximizes the adult yield while achieving quick development.