Zumstein, M. | Search bioRxiv

bioRxiv2026

A Capsid Tyrosine Residue Governs the Proteolytic Inactivation of Echovirus 11 in Lakewater

Enteroviruses are environmentally transmissible human pathogens whose stability in natural waters varies widely, yet the molecular determinants underlying this variability remain largely unknown. Echovirus 11 (E11), a re-emerging cause of severe neonatal infections, is efficiently transmitted via contaminated water, making its environmental stability a critical factor in infection risk. Here we identify a single viral capsid residue that governs E11 susceptibility to inactivation by extracellular microbial proteases in freshwater. By combining virus decay measurements in lakewater with proteolytic-cleavage profiling, viral capsid structural analyses, and reverse genetics, we show that the presence of VP2.Y97 renders E11 highly sensitive to microbially-mediated proteolytic decay. Strikingly, this residue is absent from multiple enteroviruses with greater environmental stability, indicating that substitution at a single capsid position is sufficient to shift virus fate in natural waters. These findings reveal that fine-scale capsid architecture controls virus-microbe interactions in aquatic environments and establish a molecular mechanism linking capsid variation to environmental transmission potential among enteroviruses.

microbiology↗

bioRxiv2025

Proteolytic Activity and Substrate Specificity of Lake Geneva

Heterotrophic microorganisms in lakewater secrete proteases which contribute to the turnover of dissolved organic matter and the degradation of peptidic contaminants. However, little is known about the identities and substrate specificities of these proteases. Herein, we sought to characterize the global proteolytic fingerprint of the extracellular proteases present in Lake Geneva, the largest freshwater body in Central Europe. Using Multiplex Substrate Profiling by Mass Spectrometry (MSP-MS), we identified preferred enzymatic cleavage next to positively charged and certain non-polar amino acids, while cleavage next to negatively charged residues was disfavored. Specifically, many of the detected cleavage sites were predominantly surrounded by arginine and lysine, consistent with a trypsin-like substrate specificity. This pattern was conserved across seasons and water depths and were shared with two other Swiss lakes. In contrast, we observed variability in the number and types of cleavage sites across samples, suggesting spatial and temporal differences in overall protease diversity. Using class-specific inhibitors, we found that serine and metalloproteases contribute to both exo- and endo-proteolytic activity in lakewater. Our findings expand our understanding of protein stability in lake ecosystems and may be used to predict the fate of peptidic contaminants in the environment.

microbiology↗