Biology subjects

Gonzalez-Magana, A.

Publications and source records attributed to Gonzalez-Magana, A..

3 recordsLinked to original sources

bioRxiv2025

PAF15 stabilizes PCNA on DNA and slows down its sliding dynamics

The PCNA-associated factor 15 (PAF15) protein is essential for human genome stability by regulating DNA replication and repair through its interaction with proliferating cell nuclear antigen (PCNA). Despite its significance, the mechanistic details of the PAF15-PCNA interaction remain insufficiently understood. Here, we reveal how PAF15 influences the sliding dynamics and function of PCNA. Using single-molecule diffusion analysis on a DNA skybridge platform, we show that PAF15 binding stabilizes PCNA in its DNA-bound state, reduces its diffusion rate along the duplex, restricts accessibility to PCNA PIP-box binding sites, and regulates PCNA loading and unloading on DNA via replication factor C (RFC). Our results are consistent with its coordinating role in both high-fidelity replication and lesion bypass. These findings establish PAF15 as a key regulator of PCNA function, serving as a mobile platform for DNA-editing enzymes and thereby influencing genome maintenance.

biophysics↗

bioRxiv2025

The Pseudomonas aeruginosa Tse4 toxin assembles ion-selective and voltage-sensitive ion channels to couple membrane depolarisation with K+ efflux

Pseudomonas aeruginosa employs the Type VI secretion system (T6SS) to outcompete other bacteria in its environment. Among the effectors secreted by the T6SS of P. aeruginosa PAO1, Tse4 is known for its potent antibacterial activity. This study elucidates the molecular function of Tse4, which promotes cell depolarisation in competing bacteria. Our results show that Tse4 spontaneously incorporates into lipid monolayers and forms multiionic channels in planar bilayers, with either ohmic conduction or diode-like rectifying currents and a preference for cations over anions. These observations allow us to propose a model of action whereby Tse4 channels couple cell depolarisation with K+ efflux. These insights into Tse4s pore-forming activity enhance our understanding of bacterial competition and exemplify a finely tuned antibacterial strategy, coupling its ability to cause membrane depolarisation with potassium efflux that synergises with other T6SS effectors. These results highlight the sophistication of Pseudomonas aeruginosas competitive arsenal.

microbiology↗

bioRxiv2025

Tke5 is a novel Pseudomonas putida toxin that depolarises membranes killing plant pathogens

The soil bacterium Pseudomonas putida injects toxic proteins into neighbouring competitors, including resilient phytopathogens, using the Type VI secretion system (T6SS). The secretion of toxins endows P. putida with a significant fitness advantage, allowing this biocontrol agent to thrive in plant-related polymicrobial environments and prevent phytopathogen infections. Despite its agricultural significance, the toxin repertoire of P. putida, particularly those secreted via the K2- and K3-T6SSs, remains poorly understood. We present the first comprehensive molecular study of Tke5, a potent toxin encoded within the K3-T6SS, which represents the first comprehensive functional analysis of the BTH_I2691 protein family. Our biophysical data demonstrate that Tke5 is a pore-forming toxin that disrupts bacterial membranes through selective ion transport, inducing membrane depolarisation and cell death. Unlike conventional detergent-like pore-forming toxins, Tke5 preserves overall membrane integrity, avoiding large, non-specific disruptions. This unique mechanism offers a powerful approach to targeting resilient phytopathogens. This study reveals a previously undescribed mode of action within a widespread yet understudied toxin family. Our findings highlight the potential of P. putida as a biocontrol agent, offering alternatives to chemical pesticides by exploiting novel toxin mechanisms. Understanding these bacterial toxins is crucial for developing effective strategies to combat plant pathogens.

microbiology↗