The
ADP-ribosyl
transferase activity of P. aeruginosa PE24 moiety expressed by E. coli BL21 (DE3) was assessed on nitrobenzylidene
aminoguanidine (
NBAG) and in vitro cultured
cancer cell lines. Gene encoding PE24 was isolated from P. aeruginosa isolates, cloned into pET22b( +) plasmid, and expressed in E. coli BL21 (DE3) under
IPTG induction. Genetic recombination was confirmed by colony PCR, the appearance of insert post digestion of engineered construct, and
protein electrophoresis using
sodium dodecyl-sulfate polyacrylamide gel (SDS-PAGE). The chemical compound
NBAG has been used to confirm PE24 extract
ADP-ribosyl
transferase action through UV spectroscopy, FTIR, c13-NMR, and HPLC before and after low-dose gamma irradiation (5, 10, 15, 24 Gy). The cytotoxicity of PE24 extract alone and in combination with
paclitaxel and low-dose gamma radiation (both 5 Gy and one shot 24 Gy) was assessed on adherent cell lines HEPG2, MCF-7, A375, OEC, and Kasumi-1 cell
suspension. Expressed PE24 moiety
ADP-ribosylated
NBAG as revealed by structural changes depicted by FTIR and NMR, and the surge of new peaks at different retention times from
NBAG in HPLC chromatograms. Irradiating recombinant PE24 moiety was associated with a reduction in
ADP-ribosylating activity. The PE24 extract IC50 values were < 10 μg/ml with an acceptable R2 value on
cancer cell lines and acceptable cell viability at 10 μg/ml on normal OEC. Overall, the synergistic effects were observed upon combining PE24 extract with low-dose
paclitaxel demonstrated by the reduction in IC50 whereas antagonistic effects and a rise in IC50 values were recorded after irradiation by low-dose gamma rays. KEY POINTS: • Recombinant PE24 moiety was successfully expressed and biochemically analyzed. • Low-dose gamma radiation and
metal ions decreased the recombinant PE24 cytotoxic activity. • Synergism was observed upon combining recombinant PE24 with low-dose
paclitaxel.