Biology subjects

Madigou, C.

Publications and source records attributed to Madigou, C..

3 recordsLinked to original sources

bioRxiv2026

F1F0-ATP-synthase subunit b head-to-head interactions shape intracellular membranes in Escherichia coli

1Intracellular membrane (ICM) compartments in bacteria remain poorly understood. In Escherichia coli, ICMs form upon the overproduction of certain membrane proteins. Here, we investigate at the molecular level how overproduction of subunit b of the F1Fo-ATP synthase complex shapes ICMs. Through a combination of subunit b deletions, electron microscopy, and biochemical analyses, we demonstrate that ICMs network structuration is mediated by the C-terminal domain of subunit b. High-resolution cryo-electron tomography and molecular dynamics simulations reveal that this domain forms tetrameric assemblies, bridging membranes and maintaining a regular 26 nm spacing. Transcriptomic and proteomic analyses further show that the cell responds to ICMs formation by upregulating energy metabolism genes and the ESCRT-III homolog PspA, while downregulating ribosomal and translational machinery. These results uncover a novel mechanism by which the C-terminal domain of subunit b drives the structuring of intracellular membranes. Additionally, they highlight how E. coli adapts to membrane stress by overexpressing membrane-remodeling proteins, a response that shares similarities with intracellular membrane homeostasis mechanisms in photosynthetic bacteria and unicellular algae.

microbiology↗

bioRxiv2023

The stromal side of cytochrome b6f complex regulates state transitions

In oxygenic photosynthesis, state transitions distribute light energy between Photosystem I and Photosystem II. This regulation involves the reduction of the plastoquinone pool, activation of the STT7 protein kinase by cytochrome b6f complex, phosphorylation and migration of Light Harvesting Complexes II (LHCII). Here we show the C-term of cyt b6 subunit acts on phosphorylation of STT7 and state transitions. We used site-directed mutagenesis of the chloroplast petB gene to truncate (remove L215b6) or elongate (add G216b6) the cyt b6 subunit. Modified complexes are devoid of heme ci and degraded by FTSH protease, revealing that salt bridge formation between cyt b6 (PetB) and subunit IV (PetD) is key to the assembly of the complex. In double mutants where FTSH is inactivated, modified cyt b6f are accumulated but the phosphorylation cascade is blocked. We also replaced the arginine interacting with heme ci propionate (R207Kb6). In this modified complex, heme ci is present but the kinetics of phosphorylation are slower. We show that highly phosphorylated forms of STT7 are accumulated transiently after reduction of the PQ pool, and represent the active forms of the protein kinase. 96% protein coverage using phosphoproteomics showed 4 new phosphorylated peptides in the kinase domain of STT7. Phosphorylation of the LHCII targets is favored at the expense of the protein kinase, and the migration of LHCII towards PSI is the limiting step for state transitions. Significance statementState transitions are regulatory mechanisms that optimize the quantum yield of photosynthesis. Chlamydomonas reinhardtii is the choice organism to study this regulation at the molecular level. Our study describes an unprecedented mechanism of stereochemical changes at the Qi site of the cytochrome b6f complex that trigger STT7 protein kinase activation through autophosphorylation.

plant biology↗

bioRxiv2020

Integrative analyses to investigate the link between microbial activity and molecules degradation during anaerobic digestion

Anaerobic digestion (AD) is a promising biological process which converts waste into sustainable energy. To fully exploit ADs capability, we need to deepen our knowledge of the microbiota involved in this complex bioprocess. High-throughput methodologies open new perspectives to investigate AD process at the molecular level, supported by recent data integration methodologies to extract relevant information. In this study, we investigated the link between microbial activity and substrate degradation in a lab-scale anaerobic co-digestion experiment, where bioreactors were fed with 9 different mixtures of three co-substrates (fish waste, sewage sludge, and grass). Samples were profiled using 16S rRNA sequencing and untargeted metabolomics. In this article, we propose a suite of multivariate tools to statistically integrate these data and identify coordinated patterns between groups of microbial and metabolic profiles specific of each co-substrate. Five main groups of features were successfully evidenced, including cadaverine degradation found to be associated with the activity of microorganisms from the order Clostridiales and the genus Methanosarcina. This study highlights the potential of data integration towards a comprehensive understanding of AD microbiota.

bioengineering↗