Dynamic nature of the quaternary structure of the vesicular stomatitis virus envelope glycoprotein

• Published in: Biochemistry (Easton) 1990-03, Vol.29 (10), p.2442-2449
• Main Authors: Lyles, Douglas S, Varela, Victor A, Parce, J. Wallace
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Centrifugation, Density Gradient; Cross-Linking Reagents; Energy Transfer; envelopes; Fluorescence; Fundamental and applied biological sciences. Psychology; Glucosides; guanine nucleotide-binding protein; Kinetics; Membrane Glycoproteins - analysis; Microbiology; Morphology, structure, chemical composition, physicochemical properties; Protein Conformation; Vesicular stomatitis Indiana virus - analysis; Viral Envelope Proteins - analysis; Virology; Virus Cultivation
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00462a002

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.