Biology subjects

Pombinho, R.

Publications and source records attributed to Pombinho, R..

3 recordsLinked to original sources

bioRxiv2026

Structural mechanism of metal-induced DNA release by an ArsR/SmtB transcriptional regulator

Metal-responsive transcriptional regulators must couple metal coordination to DNA release at the DNA-binding interface. However, the pathway connecting these states remains poorly understood. Here, we define this mechanism for the ArsR/SmtB-family repressor CadC from Listeria monocytogenes by combining crystal structures of apo, DNA-bound, and cadmium-bound states with biochemical and in vivo analyses. The DNA-bound structure reveals how CadC dimers bind sequence-specifically to operator DNA, via coordinated major-groove, wing and backbone interactions, with high-affinity binding depending on operator architecture. Cadmium is coordinated at the 3N sensor by an unusual Cys3-Met ligand set and stabilizes a DNA-incompatible conformation through remodeling of DNA-contacting elements and steric incompatibility between the ordered N-terminus and DNA. Mutational analyses show how these structural transitions link to metal-dependent transcriptional control in Listeria cells. We show that CadC binds zinc and supports zinc-responsive transcription in bacterial cells, and that host zinc availability modifies CadC-dependent infection phenotypes. Together, results reveal how metal coordination is converted into DNA release through coupled allosteric remodeling and steric exclusion, establishing a mechanism for signal-dependent transcriptional switching in ArsR/SmtB metalloregulators.

microbiology↗

bioRxiv2024

Molecular properties of RmlT, a wall teichoic acid rhamnosyltransferase that modulates Listeria monocytogenes virulence and antibiotic resistance

Wall teichoic acids (WTAs) from the major Gram-positive foodborne pathogen Listeria monocytogenes are peptidoglycan-associated glycopolymers decorated by monosaccharides that, while not essential for bacterial growth, are required for bacterial virulence and resistance to antimicrobials. Here we report the structure and function of a bacterial WTAs rhamnosyltransferase, RmlT, strictly required for L. monocytogenes WTAs rhamnosylation. In particular, we demonstrated that RmlT transfers rhamnose from dTDP-L-rhamnose to naked WTAs, and that specificity towards TDP-rhamnose is not determined by its binding affinity. Structures of RmlT with and without its substrates showed that this enzyme is a dimer, revealed the residues responsible for interaction with the substrates and that the catalytic residue pre-orients the acceptor substrate towards the nucleophilic attack to the sugar. Additionally, the structures provided indications for two potential interaction pathways for the long WTAs on the surface of RmlT. Finally, we confirmed that WTAs glycosyltransferases are promising targets for next-generation strategies against Gram-positive pathogens by showing that inactivation of the RmlT catalytic activity results in a decreased infection in vivo.

microbiology↗

bioRxiv2021

Stabilin-1 plays a protective role against Listeria monocytogenes infection through the regulation of cytokine and chemokine production and immune cell recruitment

Scavenger receptors are part of a complex surveillance system expressed by host cells to efficiently orchestrate innate immune response against bacterial infections. Stabilin-1 (STAB-1) is a scavenger receptor involved in cell trafficking, inflammation and cancer, however its role in infection remains to be elucidated. Listeria monocytogenes (Lm) is a major intracellular human food-borne pathogen causing severe infections in susceptible hosts. Using a mouse model of infection, we demonstrate here that STAB-1 controls Lm-induced cytokine and chemokine production and immune cell accumulation in Lm-infected organs. We show that STAB-1 also regulates the recruitment of myeloid cells in response to Lm infection and contributes to clear circulating bacteria. In addition, whereas STAB-1 appears to promote bacterial uptake by macrophages, infection by pathogenic Listeria induces the down regulation of STAB-1 expression and its delocalization from the host cell membrane. We propose STAB-1 as a new SR involved in the control of Lm infection through the regulation of host defense mechanisms, a process that would be targeted by bacterial virulence factors to promote infection.

microbiology↗