Dynamic nature of the quaternary structure of the vesicular stomatitis virus envelope glycoprotein.
The envelope glycoprotein (G protein) of vesicular stomatitis virus probably exists in the viral envelope as a trimer of identical subunits. Depending on the conditions of solubilization, G protein may dissociate into monomers. G protein solubilized with the detergent octyl glucoside was shown to exist as oligomeric forms by sedimentation velocity analysis and chemical cross-linking. G protein was modified with either fluorescein isothiocyanate or rhodamine isothiocyanate. Resonance energy transfer between fluorescein and rhodamine labels was observed upon mixing the two labeled G proteins in octyl glucoside. This result provided further evidence that G protein in octyl glucoside is oligomeric and indicated that the subunits are capable of exchange to form mixed oligomers. Resonance energy transfer was independent of G protein concentration in the range examined (10-80 nM) and was not observed when labeled G proteins were mixed with fluorescein or rhodamine that was not conjugated to protein. Resonance energy transfer decreased upon incorporation of G protein into Triton X-100, consistent with sedimentation velocity data that G protein in Triton X-100 is primarily monomeric. Kinetic analysis showed that the subunit exchange reaction had a half-time of about 3 min at 27 degrees C that was independent of G protein concentration. These data indicate that the exchange occurs through dissociation of G protein trimers into monomers and dimers followed by reassociation into timers. Thus, in octyl glucoside, G protein must exist as an equilibrium between monomers and oligomers. This implies that monomers are capable of self-assembly into trimers.
Lyles
D S
DS
Department of Microbiology and Immunology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103.
Varela
V A
VA
Parce
J W
JW
D002499:Centrifugation, Density Gradient; D003432:Cross-Linking Reagents; D004735:Energy Transfer; D005453:Fluorescence; D005960:Glucosides; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000032:analysis*; D011487:Protein Conformation; D014721:Vesicular stomatitis Indiana virus / Q000032:analysis*; D014759:Viral Envelope Proteins / Q000032:analysis*; D014776:Virus Cultivation
D003432:Cross-Linking Reagents; C028391:G protein, vesicular stomatitis virus; D005960:Glucosides; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; C018619:octyl-beta-D-glucoside