Biology subjects

Gaday, Q.

Publications and source records attributed to Gaday, Q..

5 recordsLinked to original sources

bioRxiv2025

Mechanistic insights into the allosteric regulation of cell wall hydrolase RipA in Mycobacterium tuberculosis.

D,L-endopeptidase RipA is the major PG hydrolase required for daughter cell separation in Mycobacterium tuberculosis (Mtb), as RipA defects severely hinder cell division and increase antibiotic vulnerability. Despite extensive studies, the mechanisms governing Mtb RipA regulation remain controversial and poorly understood. Here, we report an integrative structural and functional analysis of the SteAB system, a regulatory complex that has been shown to modulate cell separation in the model organism Corynebacterium glutamicum (Cglu) and is conserved across Mycobacteriales. Although Mtb SteB was previously proposed to act as a mycobacterial outer membrane copper transporter, the crystal structures of the homodimeric protein, alone and in complex with the RipA coiled-coil (CC) domain, rule out this hypothesis. Instead, the high-affinity SteB-RipA interaction, together with computational and biophysical data, strongly supports the role of SteB as a direct RipA activator that releases enzyme autoinhibition upon complex formation. In addition, crystallographic characterization of the cytoplasmic core of SteA revealed a homodimeric organization harboring a conserved functional pocket similar to the phosphonucleotide-binding site of thiamine pyrophosphokinase. These data, coupled with the in vivo phenotypic analysis of a steAB knockout mutant of Cglu, support a model in which the transmembrane SteAB heterotetramer, driven by cytoplasmic ligand binding, orchestrates the productive periplasmic positioning of RipA, leading to PG hydrolysis activation. These findings shed new light on the regulation of mycobacterial cell wall remodeling, with implications for understanding Mtb pathogenesis and identifying novel antimicrobial targets.

microbiology↗

bioRxiv2023

Eukaryotic-like gephyrin and cognate membrane receptor coordinate corynebacterial cell division and polar elongation.

The order Corynebacteriales includes major industrial and pathogenic actinobacteria such as Corynebacterium glutamicum or Mycobacterium tuberculosis. Their elaborate multi-layered cell wall, composed primarily of the mycolyl-arabinogalactan-peptidoglycan complex, and their polar growth mode impose a stringent coordination between the septal divisome, organized around the tubulin-like protein FtsZ, and the polar elongasome, assembled around the tropomyosin-like protein Wag31. Here, we report the identification of two new divisome members, a gephyrin-like repurposed molybdotransferase (GLP) and its membrane receptor (GLPR). We show that the interplay between the GLPR/GLP module, FtsZ and Wag31 is crucial for orchestrating cell cycle progression. Our results provide a detailed molecular understanding of the crosstalk between two essential machineries, the divisome and elongasome, and reveal that Corynebacteriales have evolved a protein scaffold to control cell division and morphogenesis similar to the gephyrin/GlyR system that in higher eukaryotes mediates synaptic signaling through network organization of membrane receptors and the microtubule cytoskeleton.

microbiology↗

bioRxiv2020

Population genomics and antimicrobial resistance in Corynebacterium diphtheriae

Corynebacterium diphtheriae, the agent of diphtheria, is a genetically diverse bacterial species. Although antimicrobial resistance has emerged against several drugs including first-line penicillin, the genomic determinants and population dynamics of resistance are largely unknown for this neglected human pathogen. Here we analyzed the associations of antimicrobial susceptibility phenotypes, diphtheria toxin production and genomic features in C. diphtheriae. We used 247 strains collected over several decades in multiple world regions, including the 163 clinical isolates collected prospectively from 2008 to 2017 in France mainland and overseas territories. Phylogenetic analysis revealed multiple deep-branching sublineages, grouped into a Mitis lineage strongly associated with diphtheria toxin production, and a tox-negative Gravis lineage with few tox+ exceptions including the 1990s ex-Soviet Union outbreak strain. The distribution of susceptibility phenotypes allowed proposing ecological cutoffs for most of the 19 agents tested, thereby defining acquired antimicrobial resistance. Penicillin resistance was found in 17.2% of prospective isolates. Four isolates were multidrug resistant (>8 agents), including to penicillin and macrolides. Homologous recombination was frequent (r/m = 5) and horizontal gene transfer contributed to the emergence of antimicrobial resistance in multiple sublineages. Genome-wide association mapping uncovered genetic factors of resistance, including an accessory penicillin-binding protein (PBP2m) located in diverse genomic contexts. Gene pbp2m is widespread in other Corynebacterium species and its expression in C. glutamicum demonstrated its effect against several beta-lactams. A novel 73-kb C. diphtheriae multi-resistance plasmid was discovered. This work uncovers the dynamics of antimicrobial resistance in C. diphtheriae in the context of phylogenetic structure, biovar and diphtheria toxin production, and provides a blueprint to analyze re-emerging diphtheria.

microbiology↗

bioRxiv2020

Central role and structure of the membrane pseudokinase YukC in the antibacterial Bacillus subtilis Type VIIb Secretion System.

Type VIIb Secretion System (T7SSb) has been recently identified in Firmicutes resembling the mycobacterial T7SSa. Despite limited sequence homology, T7SSa and T7SSb have substrates with striking structural similarities, the WXG100 proteins. Recent advances in Staphylococcus spp. proposed that T7SSb is involved in intra-species competition. However, the architecture and mechanism of action of this secretion complex remain largely obscure. Here, we investigate the T7SSb of Bacillus subtilis as a model system. We report the first evidence of B. subtilis ability to mediate intra- and inter-species antibacterial activity in a T7SSb-dependent manner. Then, we present the first systematic investigation of the T7SSb protein-protein network, revealing novel interactions and highlighting the central role of the pseudokinase subunit YukC in the assembly of the system. Its direct interaction with a T7SSb-secreted toxin supports its role in recruiting substrates to the secretion machinery. Finally, we solved the crystal structure of full-length transmembrane YukC defining novel structural motifs and suggesting that intrinsic flexibility modulates the orientation of the pseudokinase domains and YukC function. Overall, our results provide a better understanding on the role and molecular organisation of the T7SSb, opening new perspectives for the comprehension of this poorly characterized molecular machine.

microbiology↗

bioRxiv2019

Essential dynamic interdependence of FtsZ and SepF for Z-ring and septum formation in Corynebacterium glutamicum

The mechanisms of Z-ring assembly and regulation in bacteria are poorly understood, particularly in non-model organisms. Actinobacteria, one of the largest bacterial phyla that includes the deadly human pathogen Mycobacterium tuberculosis, lack the canonical FtsZ-membrane anchors as well as all positive and negative Z-ring regulators described for E. coli. Here we investigate the physiological function of Corynebacterium glutamicum SepF, the only cell division-associated protein from Actinobacteria known to directly interact with the conserved C-terminal tail of FtsZ but whose actual mode of action in cytokinesis is yet to be elucidated. We used a mechanistic cell biology approach to unveil the essential interdependence of FtsZ and SepF required for the formation of a functional Z-ring in the actinobacterial model organism C. glutamicum. The crystal structure of the SepF-FtsZ complex reveals a hydrophobic FtsZ-binding pocket, which defines the SepF homodimer as the functional unit, and a reversible oligomerization interface regulated via an alpha helical switch. FtsZ filaments and lipid membranes have opposing effects on SepF polymerization, leading to a complex dynamic role of the protein at the division site, involving FtsZ bundling, Z-ring tethering and membrane reshaping activities that are needed for proper Z-ring assembly and function.

microbiology↗