Updated FTP location. Medusavirus particles was resuspended in PBS containing 0.5% SDS and protease inhibitor cocktail (Nacalai Tesque, Japan) and incubated for 1 h at 65°C. Samples were subjected to trichloroacetic acid (TCA) precipitation, followed by protein quantification using the BCA method. Proteins were reduced for 2 h at 37°C, and subsequently alkylated using iodoacetamide for 30 min at 20 to 25°C (room temperature), followed by treatment with trypsin for 20 h at 37°C. After desalination and concentration, the treated proteins were subjected to LC–MS/MS analysis using EASY-nLC 1200 (Thermo Fisher Scientific Inc., USA) and Q Exactive Plus (Thermo Fisher Scientific Inc., USA).