Comparative Venomics of the Vipera ammodytes transcaucasiana and Vipera ammodytes montandoni from Turkey Provides Insights into Kinship.

The Nose-horned Viper () is one of the most widespread and venomous snakes in Europe, which causes high frequent snakebite accidents. The first comprehensive venom characterization of the regional endemic Transcaucasian Nose-horned Viper () and the Transdanubian Sand Viper () is reported employing a combination of intact mass profiling and bottom-up proteomics. The bottom-up analysis of both subspecies identified the major snake protein families of viper venoms. Furthermore, intact mass profiling revealed the presence of two tripeptidic metalloprotease inhibitors and their precursors. While previous reports applied multivariate analysis techniques to clarify the taxonomic status of the subspecies, an accurate classification of is still part of the ongoing research. The comparative analysis of the viper venoms on the proteome level reveals a close relationship between the subspecies, which could be considered to clarify the classification of the Transcaucasian Nose-horned Viper. However, the slightly different ratio of some venom components could be indicating interspecific variations of the two studied subspecies or intraspecies alternations based on small sample size. Additionally, we performed a bioactivity screening with the crude venoms against several human cancerous and non-cancerous cell lines, which showed interesting results against a human breast adenocarcinoma epithelial cell line. Several fractions of demonstrated a strong cytotoxic effect on triple negative MDA MB 231 breast cancer cells.