Antigenic Variants Of Bovine Leukemia-Virus (Blv) Are Defined By Amino-Acid Substitutions In The Nh2 Part Of The Envelope Glycoprotein-Gp51

Bovine leukemia virus (BLV) p24 gene was expressed in Saccharomyces cerevisiae
under the control of the PHO5 (encoding repressible acid phosphatase, rAPase)
promoter. Yeast cells were transformed by a yeast-E. coli shuttle vector carrying
the PHO5 promoter, the p24 gene and the CYC1 transcription terminator. After low
inorganic phosphate (Pi) induction of the PHO5 promoter, p24 accumulated in the
producing cells up to a concentration representing 10% of total soluble proteins.
The expression level of p24 gene was not increased by insertion of the positive
regulatory gene PHO4 on the p24 expression vector. The p24 produced in this
system and incubated in crude yeast extract showed a remarkably high resistance
to proteolytic degradation, a feature that presumably correlates with the compact
globular conformation of the protein combined to the stabilizing effect of the
N-terminal residue.