Biology subjects

Bento, I.

Publications and source records attributed to Bento, I..

3 recordsLinked to original sources

bioRxiv2025

Activity regulation of a glutamine amidotransferase bienzyme complex by substrate-induced subunit interface expansion

Glutamine amidotransferases are multienzyme machineries in which reactive ammonia is generated by a glutaminase and then transferred through a sequestered protein tunnel to a synthase active site for incorporation into diverse metabolites. To avoid wasteful metabolite consumption, there is a requirement for synchronized catalysis but any generally applicable mechanistic insight is still lacking. As synthase activity depends on glutamine turnover, we investigated possible mechanisms controlling glutaminase catalysis, using aminodeoxychorismate synthase involved in folate biosynthesis as a model. By analyzing this system in distinct states of catalysis, we found that incubation with glutamine leads to a subunit interface expansion by one third of its original area. These changes completely enclose the glutaminase active site for sequestered catalysis and subsequent transport of volatile ammonia to the synthase active site. In view of similar rearrangements in other glutamine amidotransferases, our observations provide a general mechanism for catalysis synchronization of this multienzyme family.

biochemistry↗

bioRxiv2024

Subtleties in Clathrin Heavy Chain Binding Boxes provide selectivity among Adaptor Proteins of Budding Yeast

Clathrin, forming the triskelion network, orchestrates highly regulated cellular processes facilitating cargo internalization and trafficking in eukaryotes, with its N-terminal domain (NTD) pivotal for adaptor protein (AP) interactions. The NTD contains up to four AP-binding sites, and their roles in preferential occupancy by APs have not been addressed. Here, employing a combination of integrative biophysical and structural approaches together with in vivo functional experiments, we investigated the binding hierarchy and selectivity of adaptors for clathrin, aiming to understand the evolutionary conservation of redundant APs and their specialized roles in endocytosis and cellular trafficking mechanisms. We found that yeast epsin Ent5 displayed the highest affinity for clathrin, indicating its significant role in cellular trafficking processes. Epsins Ent1 and Ent2, which are crucial for endocytosis but described to have redundant functions, revealed distinct binding patterns; Ent1 demonstrated stronger interactions with clathrin than Ent2, explaining its functional divergence towards actin binding. Despite both having actin anchoring domains, since Ent1 is actually more stably recruited by clathrin, it would provide a better actin anchoring function. These results offer molecular insights into AP selectivity, suggesting they competitively bind clathrin while also targeting different clathrin sites.

molecular biology↗

bioRxiv2024

Circadian rhythms mediate malaria transmission potential

Malaria transmission begins when infected female Anopheles mosquitos deposit Plasmodium parasites into the mammalian hosts skin during a bloodmeal. The salivary gland-resident sporozoite parasites migrate to the bloodstream, subsequently invading and replicating within hepatocytes. As Anopheles mosquitos are more active at night, with a 24-hour rhythm, we investigated whether their salivary glands are under circadian control, anticipating bloodmeals and modulating sporozoite biology for host encounters. Here we show that approximately half of the mosquito salivary gland transcriptome, particularly genes essential for efficient bloodmeals such as anti-blood clotting factors, exhibits circadian rhythmic expression. Furthermore, we demonstrate that mosquitoes prefer to feed during nighttime, with the amount of blood ingested varying cyclically throughout the day. Notably, we show a substantial subset of the sporozoite transcriptome cycling throughout the day. These include genes involved in parasite motility, potentially modulating the ability to initiate infection at different times of day. Thus, although sporozoites are typically considered quiescent, our results demonstrate their transcriptional activity, revealing robust daily rhythms of gene expression. Our findings suggest a circadian evolutionary relationship between the vector, parasite and mammalian host that together modulate malaria transmission.

microbiology↗