PURIFICATION OF RECOMBINANT BUDGERIGAR FLEDGLING DISEASE VIRUS VP1 CAPSID PROTEIN AND ITS ABILITY FOR IN-VITRO CAPSID ASSEMBLY

A recombinant system for the major capsid VP1 protein of budgerigar fl edgling disease virus has been established. The VPI gene was inserted into a truncated form of the pFlag-1 vector and expressed in Escherich ia coli. The budgerigar fledgling disease virus VP1 protein was purifi ed to near homogeneity by immunoaffinity chromatography. Fractions con taining highly purified VP1 were pooled and found to constitute 3.3% o f the original E. coli-expressed VP1 protein. Electron microscopy reve aled that the VP1 protein was isolated as pentameric capsomeres. Elect ron microscopy also revealed that capsid-like particles were formed in vitro from purified VP1 capsomeres with the addition of Ca2+ ions and the removal of chelating and reducing agents.