A central event in the pathogenesis of Alzheimer’s disease (AD) is the accumulation of senile plaques composed of aggregated amyloid-β (Aβ) peptides. The main class of drugs currently used for the treatment of AD are the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. In this study, it has been shown that Aβ augmented AChE activity in vitro, maximum activation of 548 ± 5% was achieved following 48 h of incubation with 10 μM of Aβ_1–40, leading to a 7.7-fold increase in catalytic efficiency. The observed non-competitive type of AChE activation by Aβ_1–40 was associated with increased V_max and unchanged K_m. Although BChE activity also increased following incubation with Aβ_1–40, this was less efficiently achieved as compared with AChE. Ex vivo electrophysiological experiments showed that 10 μM of Aβ_1–40 significantly decreased the effect of the AChE inhibitor huperzine A on the synaptic potential parameters.

BTB (bric-a-brack, Tramtrack, and broad complex) is a diverse group of protein-protein interaction domains found within metazoan proteins. Transcription factors contain a dimerizing BTB subtype with a characteristic N-terminal extension. The Tramtrack group (TTK) is a distinct type of BTB domain, which can multimerize. Single-particle cryo-EM microscopy revealed that the TTK-type BTB domains assemble into a hexameric structure consisting of three canonical BTB dimers connected through a previously uncharacterized interface. We demonstrated that the TTK-type BTB domains are found only in Arthropods and have undergone lineage-specific expansion in modern insects. The Drosophila genome encodes 24 transcription factors with TTK-type BTB domains, whereas only four have non-TTK-type BTB domains. Yeast two-hybrid analysis revealed that the TTK-type BTB domains have an unusually broad potential for heteromeric associations presumably through a dimer-dimer interaction interface. Thus, the TTK-type BTB domains are a structurally and functionally distinct group of protein domains specific to Arthropodan transcription factors.

Cyanobacteria use soluble antenna megacomplexes, phycobilisomes (PBSs), to maximize light-harvesting efficiency and small photoswitchable orange carotenoid proteins (OCPs) to down-regulate PBSs in high light. Among known PBS morphologies, the one from the basal cyanobacterial genus Gloeobacter still lacks detailed structural characterization. Here, we reconstructed a cryo–electron microscopy structure of the >10-megadalton Gloeobacter violaceus PBS, with diverging, conformationally mobile bundles of rods composed of stacked phycoerythrin and phycocyanin hexamers, stemming from a pentacylindrical allophycocyanin core belted by auxiliary phycocyanin hexamers. We show how two Gloeobacter -specific multidomain linker proteins, Glr1262 and Glr2806, maintain this bundle-shaped architecture and reveal its differential regulation via nonphotochemical quenching by two OCP types of G. violaceus that recognize separate binding sites within the allophycocyanin core, including lateral cylinders absent in tricylindrical cores.

BTB (Bric-a-brack, Tramtrack and Broad Complex) is a diverse group of protein-protein interaction domains found within metazoan proteins. Transcription factors contain a dimerizing BTB subtype with a characteristic N-terminal extension. The Tramtrack group (TTK) is a distinct type of BTB domain, which can multimerize. Single-particle cryo-EM microscopy revealed that the TTK-type BTB domains assemble into a hexameric structure consisting of three canonical BTB dimers connected through a previously uncharacterized interface. We demonstrated that the TTK-type BTB domains are found only in Arthropods and have undergone lineage-specific expansion in modern insects. The Drosophila genome encodes 24 transcription factors with TTK-type BTB domains, whereas only four have non-TTK-type BTB domains. Yeast two-hybrid analysis revealed that the TTK-type BTB domains have an unusually broad potential for heteromeric associations presumably through dimer-dimer interaction interface. Thus, the TTK-type BTB domains are a structurally and functionally distinct group of protein domains specific to Arthropodan transcription factors.

Cyanobacteria use soluble antenna megacomplexes, phycobilisomes (PBS), to maximize light-harvesting efficiency and small photoswitchable orange carotenoid proteins (OCPs) to down-regulate PBS in high light. Among known PBS morphologies, the one from the basal cyanobacterial genus Gloeobacter still lacks detailed structural characterization. Here, we present the cryo-EM structure of the G. violaceus PBS, a >10-MDa complex with a unique architecture consisting in 516 polypeptide chains totaling nearly 90,000 residues and harboring over 860 bilin chromophores. This unique PBS features diverging, conformationally mobile bundles of rods composed of stacked phycoerythrin and phycocyanin hexamers, stemming from a pentacylindrical allophycocyanin core belted by auxiliary phycocyanin hexamers. We show how two Gloeobacter -specific multidomain linker proteins, Glr1262 and Glr2806, maintain this bundle-shaped architecture and reveal its differential regulation via non-photochemical quenching by two OCP types of G. violaceus that recognize separate binding sites within the allophycocyanin core, including lateral cylinders absent in tricylindrical cores. Our findings provide the high-resolution structural insight into Gloeobacter PBS and its regulation, revealing divergent adaptations in early-branching cyanobacteria. The structure advances understanding of PBS diversity and evolution, offering a framework for bioengineering light-harvesting systems in synthetic biology and biotechnological applications.