Deletions in the transmembrane domain of a sindbis virus glycoprotein alter virus infectivity, stability, and host range.

The alphaviruses are composed of two icosahedral protein shells, one nested within the other. A membrane bilayer derived from the host cell is sandwiched between the protein shells. The protein shells are attached to one another by protein domains which extend one of the proteins of the outer shell through the membrane bilayer to attach to the inner shell. We have examined the interaction of the membrane-spanning domain of one of the membrane glycoproteins with the membrane bilayer and with other virus proteins in an attempt to understand the role this domain plays in virus assembly and function. Through incremental deletions, we have reduced the length of a virus membrane protein transmembrane domain from its normal 26 amino acids to 8 amino acids. We examined the effect of these deletions on the assembly and function of virus particles. We found that progressive truncations in the transmembrane domain profoundly affected production of infectious virus in a cyclic fashion. We also found that membrane composition effects protein-protein and protein-membrane interactions during virus assembly.