MEMBRANE ORIENTATION AND OLIGOMERIZATION OF THE SMALL HYDROPHOBIC PROTEIN OF HUMAN RESPIRATORY SYNCYTIAL VIRUS

Previous work has demonstrated that the small hydrophobic (SH) protein of human respiratory syncytial virus (RSV) A2 strain is a 64 amino ac id integral membrane protein that accumulates intracellularly as an un glycosylated major species (SH0), a minor species truncated at the ami no terminus and two N-glycosylated species one of which contains a fur ther addition of polylactosamine. In this study, the membrane orientat ion of SH0 was mapped by trypsinization of intact RSV-infected cells f ollowed by washout, lysis and immunoprecipitation of protected fragmen ts with antisera specific for the protein termini. This showed that th e C terminus is extracellular and the SH protein was not detectably pa lmitylated. Analysis of the SH protein by sedimentation on sucrose gra dients showed that it rapidly assembles into a homo-oligomer that cose diments with the F protein tetramer. Interestingly, all forms of the S H protein were found in the oligomeric fraction. Chemical cross-linkin g generated species which appeared to represent dimers, trimers, tetra mers and pentamers as well as a minor species of 180K which might corr espond to the oligomeric form detected by sucrose gradient sedimentati on.