Molecular mechanism of glutaminase activation through filamentation and the role of filaments in mitophagy protection.

Glutaminase (GLS), which deaminates glutamine to form glutamate, is a mitochondrial tetrameric protein complex. Although inorganic phosphate (Pi) is known to promote GLS filamentation and activation, the molecular basis of this mechanism is unknown. Here we aimed to determine the molecular mechanism of Pi-induced mouse GLS filamentation and its impact on mitochondrial physiology. Single-particle cryogenic electron microscopy revealed an allosteric mechanism in which Pi binding at the tetramer interface and the activation loop is coupled to direct nucleophile activation at the active site. The active conformation is prone to enzyme filamentation. Notably, human GLS filaments form inside tubulated mitochondria following glutamine withdrawal, as shown by in situ cryo-electron tomography of cells thinned by cryo-focused ion beam milling. Mitochondria with GLS filaments exhibit increased protection from mitophagy. We reveal roles of filamentous GLS in mitochondrial morphology and recycling.

Citrus essential oil: would it be feasible as antimicrobial in the bioethanol industry?

Essential oils (EOs) extracted from Citrus peels contain 85%-99% volatile components (a mixture of monoterpenes, sesquiterpenes, and their oxygenated derivatives) and 1%-15% non-volatile compounds. Citrus EOs have been long known for their antimicrobial properties, owing to which these EOs have a diverse range of applications. However, no studies have reported the applicability of Citrus EOs for the control of bacterial and yeast contaminants in the bioethanol industry. In this regard, the present review aimed to explore the feasibility of Citrus EOs in this industry. The Web of Science database was searched for reports that described the association of Citrus EOs with the most common microorganisms in the bioethanol industry to evaluate the efficacy of these EOs as antimicrobial agents in this context. The objective of the review was to suggest a novel antimicrobial that could replace sulfuric acid and antibiotics as the commonly used antimicrobial agents in the bioethanol industry. Citrus EOs exhibit antibacterial activity against Lactobacillus, which is the main bacterial genus that contaminates this fermentation process. The present report also confirms the selective action of these EOs on the contaminating yeasts and not/less on ethanol-producing yeast Saccharomyces cerevisiae, however further studies should be conducted to investigate the effects of Citrus EOs in yeast-bacterium co-culture.