Biology subjects

Eltschkner, S.

Publications and source records attributed to Eltschkner, S..

3 recordsLinked to original sources

bioRxiv2026

Repurposing a chromosome segregation ParB-CTPase fold into an ATPase toxin for contact-dependent growth inhibition in plant and animal pathogens

Bacterial competition drives the evolution of antibacterial mechanisms, yet how new activities arise remains poorly understood. A major route to innovation is the reuse of pre-existing genetic systems, whereby conserved protein modules are repurposed in new biological contexts to generate new capabilities. Here, we show that the ParB-CTPase fold, a conserved nucleotide-binding module best known for its role in chromosome segregation, can be functionally repurposed as an antibacterial toxin. We identify ToxB, a ParB-like domain embedded within the polymorphic toxin region of contact-dependent inhibition systems and show that it functions as a potent antibacterial effector. Structural and biochemical analyses reveal that ToxB retains the core architecture of the ParB-CTPase fold but lacks DNA-binding capability and preferentially binds ATP. This shift in nucleotide specificity underpins a distinct mode of action, in which ATP binding and hydrolysis trigger rapid nucleoid compaction, chromosome segregation defects, oxidative stress, cell chaining, and ultimately cell lysis. ToxB also exhibits toxic activity in plant cells, suggesting that it targets conserved cellular processes. Together, these findings provide direct experimental evidence that the ParB-NTPase fold is biologically versatile and can be repurposed for biological roles fundamentally distinct from its ancestral function in DNA segregation.

microbiology↗

bioRxiv2024

A SUMO interacting motif in the Replication initiator protein of Tomato yellow leaf curl virus is required for viral replication

CRESS-DNA viruses form a diverse group of viruses that use rolling-circle replication to replicate their genomes. They infect organisms in almost all branches of the eukaryotic tree of life. All CRESS-DNA viruses have one protein in common, the Replication initiator protein (Rep), which orchestrates viral replication using the host DNA replication machinery. In the case of the plant-infecting Geminiviridae, this multifunctional protein both recruits the host DNA replication machinery and manipulates posttranslational modification including Small ubiquitin-like modifier (SUMO) conjugation. In fact, Rep from two different geminiviruses, Tomato yellow leaf curl virus (TYLCV) and Tomato golden mosaic virus (TGMV), was shown to interact with the SUMO conjugating enzyme SCE1. Here, we demonstrate that also TYLCV Rep interacts with Arabidopsis SUMO1 and report on a SUMO interacting motif (SIM) in the SF3 helicase domain of Rep. Remarkably, an intact SIM proved to be important for the interaction of Rep with both SUMO1 and SCE1. The same motif was also essential for viral replication and Rep ATPase activity. Our findings thus connect the interaction between Rep and the SUMO machinery with viral replication of TYLCV. ImportanceThe identification of a non-canonical SUMO-interacting motif (SIM) within the Rep protein of Tomato yellow leaf curl virus (TYLCV) reveals a connection between viral replication and a protein modification, SUMOylation. Importantly, the motif was found to be conserved between Rep proteins from different geminiviruses. Functionally, the motif was critical for the interaction of Rep with proteins of the SUMO machinery, viral DNA replication, and Rep ATPase acitvity. In particular, the third position of the motif was important for each of these activities. We thus uncover a novel mechanism on how geminiviruses recruit the SUMO machinery likely to their own need.

plant biology↗

bioRxiv2023

Extraordinary peptide-binding mode of a songbird MHC class-I molecule suggests mechanism to counter pathogen immune evasion

Long-distance migratory animals such as birds and bats have evolved to withstand selection imposed by pathogens across the globe, and pathogen richness is known to be particularly high in tropical regions. Immune genes, so-called Major Histocompatibility Complex (MHC) genes, are highly duplicated in songbirds compared to other vertebrates, and this high MHC diversity has been hypothesised to result in a unique adaptive immunity. To understand the rationale behind the evolution of the high MHC genetic diversity in songbirds, we determined the structural properties of an MHC class I protein, Acar3, from a long-distance migratory songbird, the great reed warbler Acrocephalus arundinaceus (in short: Acar). The structure of Acar3 was studied in complex with pathogen-derived antigens and shows an overall antigen presentation similar to human MHC class I. However, the peptides bound to Acar3 display an unusual conformation: Whereas the N-terminal ends of the peptides display enhanced flexibility, the conformation of their C-terminal halves is rather static. This uncommon peptide-binding mode in Acar3 is facilitated by a central Arg residue within the peptide-binding groove that fixes the backbone of the peptide at its central position, and potentially permits successful interactions between MHC class I and innate immune receptors. Our study highlights the importance of investigating the immune system of wild animals, such as birds and bats, to uncover unique immune mechanisms which may neither exist in humans nor in model organisms.

ecology↗