The structure and function of the HE protein of influenza C virus

The hemagglutinin-esterase (HE) glycoprotein is an integral membrane protein and the major surface antigen of influenza C virion. It displays three biological activities: receptor-binding activity for N-acetyl-9-O-acetylneuraminic acid, fusion with the host cell membrane, and receptor-destroying activity which is a neuraminate-O-acetylesterase. This protein undergoes four kinds of posttranslational processing: proteolytic cleavage, N-glycosylation, fatty acid acylation, and phosphorylation. We summarize here the data concerning the sites on the HE molecule responsible for the biological activities including antigenic epitopes as well as those concerning the role of posttranslational modifications in virus replication.