Altered E2 glycoprotein of Sindbis virus and its use in complementation studies

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Abstract
A Sindbis virus variant that contains a smaller MW form of the viral glycoprotein E2 was detected. The MW of the PE2 precursor and the glycosylation pattern of the smaller E2 are normal, thus indicating that this E2 is formed by an aberrant proteolytic cleavage. The altered E2 was detected in an RNA+ temperature-sensitive mutant that was defective in proteolytic cleavage, but the abnormal PE2-to-E2 reaction could be separated from the ts mutation and is not itself a temperature-sensitive defect. The variant E2 was used as a marker to monitor the complementation reaction between an RNA+ and an RNA- mutant and discovered that complementation was reciprocal; the RNA defect was corrected by the RNA+ mutant gene products but the RNA+ defect was not complemented by and RNA- gene products. Other studies showed that the smaller E2 is not preferentially selected during viral maturation and budding. No significant changes were detected in the biological activity of virions with this altered E2 protein. Comparison of the electrophoretic migration of the E1 and E2 Sindbis viral glycoproteins in a 2 dimensional polyacrylamide slab gel system that was first run in the absence of SH-reducing reagent and then with .beta.-mercaptoethanol indicated that the mobility of E1, but not that of E2, was significantly altered by reduction.