High-level expression and purification of biologically active recombinant pokeweed antiviral protein.
Pokeweed antiviral protein (PAP) from the leaves of the pokeweed plant, Phytolacca americana, is a naturally occurring single-chain ribosome-inactivating protein, which catalytically inactivates both prokaryotic and eukaryotic ribosomes. The therapeutic potential of PAP has gained considerable interest in recent years due to the clinical use of native PAP as the active moiety of immunoconjugates against cancer and AIDS. The clinical use of native PAP is limited due to inherent difficulties in obtaining sufficient quantities of a homogenously pure and active PAP preparation with minimal batch to batch variability from its natural source. Previous methods for expression of recombinant PAP in yeast, transgenic plants and Escherichia coli have resulted in either unacceptably low yields or were too toxic to the host system. Here, we report a successful strategy which allows high level expression of PAP as inclusion bodies in E. coli. Purification of refolded recombinant protein from solubilized inclusion bodies by size-exclusion chromatography yielded biologically active recombinant PAP (final yield: 10 to 12 mg/L). The ribosome depurinating in vitro N-glycosidase activity and cellular anti-HIV activity of recombinant PAP were comparable to those of the native PAP. This expression and purification system makes it possible to obtain sufficient quantities of biologically active and homogenous recombinant PAP sufficient to carry out advanced clinical trials. To our knowledge, this is the first large-scale expression and purification of biologically active recombinant PAP from E. coli.
Biotherapy Program, Hughes Institute, St. Paul, Minnesota 55113, USA.
F
F
Rajamohan
C R
CR
Engstrom
T J
TJ
Denton
L A
LA
Engen
I
I
Kourinov
F M
FM
Uckun
D001483:Base Sequence; D015153:Blotting, Western; D002474:Cell-Free System; D002852:Chromatography, Ion Exchange; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D015497:HIV-1 / Q000187:drug effects; D009699:N-Glycosyl Hydrolases; D010940:Plant Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology; D054789:Ribosome Inactivating Proteins, Type 1
D017931:DNA Primers; D010940:Plant Proteins; D011994:Recombinant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D009699:N-Glycosyl Hydrolases; C024275:pokeweed antiviral protein