Effects of different chaperones on HPV His 6 -E6 expression levels. Representative immunoblots of induction and purification of HPV16 His 6 -E6 produced in E. coli <t>JM109.</t> a Bacterial transformation with the pQE30-HPV16 His 6 -E6 expression plasmid alone (w/o) or with the different chaperone systems (chaperones A–E, see Table 2 ). Total proteins were extracted by re-suspension in SDS-loading buffer of E. coli cell cultures, according to their OD 600 . b Purification of the HPV16 His 6 -E6 protein without chaperones (w/o) and with the trigger factor chaperone (with chaperones; chaperone E, see Table 2 ). M ColorBurst, Sigma, lanes 1 1 µL, lanes 2 3 µL, lane 3 C + , 20 ng of purified His 6 -E6 protein positive control 