MEMBRANE-PERMEABILITY CHANGES INDUCED IN ESCHERICHIA-COLI BY THE SH PROTEIN OF HUMAN RESPIRATORY SYNCYTIAL VIRUS

The small hydrophobic (SH) protein of human respiratory syncytial viru s (HRSV) has been efficiently expressed in Escherichia coli. In analog y to small hydrophobic proteins encoded by other RNA viruses, membrane permeability changes to low-molecular-weight compounds were detected in bacteria expressing HRSV SH protein. These changes implied, at leas t, the entry of both the protein synthesis inhibitor hygromycin B and the beta-galactoside substrate o-nitrophenyl-beta-D-galactopyranoside and the exit of preloaded [H-3]uridine from bacterial cells. Site-dire cted mutagenesis indicated that the C-terminal end of SH is needed for induction of membrane permeability changes. In addition, amino acid s ubstitution at residue 32 (lie to Lys) abolished that activity. This w as correlated with a drastic increase in SH electrophoretic mobility a nd a decrease of the predicted values of alpha-helix for all residues of the SH transmembrane domain. Other sequence changes have either par tial effect or no effect on the membrane permeability changes induced by the SH protein. However, none of the mutations abrogated the associ ation of SH protein with bacterial membranes, indicating that incorpor ation of SH protein to membranes is not sufficient to induce the obser ved changes. Membrane permeability changes then might provide a useful test for the identification of key amino acid residues in this unique HRSV gene product. (C) 1997 Academic Press.