Structural characterization of the E2 glycoprotein from Sindbis by lysine biotinylation and LC-MS/MS

Sindbis is an Alphavirus capable of infecting and replicating in both vertebrate and invertebrate hosts. Mature Sindbis virus particles consist of an inner capsid surrounded by a host-derived lipid bilayer, which in turn is surrounded by a protein shell consisting of the E1 and E2 glycoproteins. While a homolog of the E1 glycoprotein has been structurally characterized, the amount of structural data on the E2 glycoprotein is considerably less. In this study, the organization of the E2 glycoprotein was probed by surface biotinylation of intact virions. The virus remained fully infectious, demonstrating that the biotinylation did not alter the topology of the proteins involved in infection. Seven sites of modification were identified in the E2 glycoprotein (K70, K76, K97, K131, K149, K202, and K235), while one site of modification in the E1 glycoprotein (K16) was identified, confirming that the E1 protein is almost completely buried in the virus structure.