Protein mass Protein mass spectrometry was used to detect the degree of biotinylation of V5-APEX2-HBC-NES after adding H2O2, and to search for host factors that interact with HBV core protein.spectrometry was used to detect the degree of biotinylation of V5-APEX2-HBC-NES after adding H2O2, and to search for host factors that interact with HBV core protein.

Chronic hepatitis B virus (HBV) infection is a leading cause of liver cirrhosis and liver cancer, representing a global health problem for which a functional cure is difficult to achieve. The HBV core protein (HBc) is essential for multiple steps in the viral life cycle; it is the building block of the nucleocapsid in which viral DNA reverse transcription occurs, and it mediates viral–host cell interactions critical to HBV infection persistence. However, systematic studies targeting HBc-interacting proteins remain lacking. An engineered ascorbate peroxidase called APEX2, is genetically targeted to a cellular region of interest and biochemically labeled neighboring proteins within living cells. Cells are then lysed, and biotinylated proteins are enriched with streptavidin beads and identified by mass spectrometry.Here, we combined HBc with the engineered ascorbate peroxidase 2 (APEX2) to systematically identify HBc-related proteins in living cells.