What best describes the role of proteases in the context of virus entry into host cells?

• A. Stabilizing the viral genome
• B. Facilitating lipid membrane fusion
• C. Activating viral transcription
• D. Degrading host cell defenses

Answer: (B)

Proteases play a crucial role in the entry of viruses into host cells by facilitating lipid membrane fusion. Many viruses rely on the action of proteases to cleave specific protein sequences in their envelope glycoproteins. This cleavage is essential for the conformational changes that promote the fusion of the viral membrane with the host cell membrane. By facilitating this fusion, proteases enable the viral genome and associated proteins to enter the host cell and initiate infection.

In contrast, actions like stabilizing the viral genome or activating viral transcription are typically carried out by other viral or host factors. Degrading host cell defenses might relate to some viral strategies but is not the direct role of proteases in the entry process. Thus, the correct understanding of proteases highlights their specific function in enabling membrane fusion, which is a critical step in viral entry into host cells.