Subunit interactions of vesicular stomatitis virus envelope glycoprotein influenced by detergent micelles and lipid bilayers.
The envelope glycoprotein (G protein) of vesicular stomatitis virus is a transmembrane protein that exists as a trimer of identical subunits in the virus envelope. We have examined the effect of modifying the environment surrounding the membrane-spanning sequence on the association of G protein subunits using resonance energy transfer. G protein subunits were labeled with either fluorescein isothiocyanate or rhodamine isothiocyanate. When the labeled G proteins were mixed in the presence of the detergent octyl glucoside, mixed trimers containing both fluorescent labels were formed as a result of subunit exchange, as shown by resonance energy transfer between the two labels. In contrast when fluorescein- and rhodamine-labeled G proteins were mixed in the presence of Triton X-100, no resonance energy transfer was observed, indicating that subunit exchange did not occur in Triton X-100 micelles. However, if labeled G proteins were first mixed in the presence of octyl glucoside, energy transfer persisted after dilution with buffer containing Triton X-100. This result indicates that the G protein subunits remained associated in Triton X-100 micelles and that the failure to undergo subunit exchange was due to lack of dissociation of G protein subunits. Chemical cross-linking experiments confirmed that G protein was trimeric in the presence of Triton X-100. The efficiency of resonance energy transfer between labeled G protein was higher when G proteins were incorporated into dimyristoylphosphatidylcholine liposomes compared to detergent micelles. This result indicates that the labels exist in a more favorable environment for energy transfer in membranes than in detergent micelles.(ABSTRACT TRUNCATED AT 250 WORDS)
Wilcox
M D
MD
Department of Biochemistry, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1064.
McKenzie
M O
MO
Parce
J W
JW
Lyles
D S
DS
D003432:Cross-Linking Reagents; D003902:Detergents; D005456:Fluorescent Dyes; D005960:Glucosides; D006023:Glycoproteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins; D008823:Micelles; D017830:Octoxynol; D011092:Polyethylene Glycols; D013816:Thermodynamics; D014721:Vesicular stomatitis Indiana virus / Q000737:chemistry*; D014759:Viral Envelope Proteins / Q000737:chemistry*
D003432:Cross-Linking Reagents; D003902:Detergents; D005456:Fluorescent Dyes; C028391:G protein, vesicular stomatitis virus; D005960:Glucosides; D006023:Glycoproteins; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins; D008823:Micelles; D014759:Viral Envelope Proteins; C018619:octyl-beta-D-glucoside; D011092:Polyethylene Glycols; D017830:Octoxynol