Overexpression and purification of isotopically labeled Escherichia coli MutH for NMR studies

Purification and refolding optimization of recombinant bovine enterokinase light chain overexpressed in Escherichia coli

The nucleotide sequence encoding bovine enterokinase light chain (EK) from Chinese northern yellow bovine was isolated. Two single-nucleotide mutations, namely, C245G and A528T were identified. The gene encoding the Pro82Arg/Glu176Asp variant of known bovine EK was fused with glutathione S-transferase and overexpressed mainly as an inclusion body in Escherichia coli BL21 (DE3), upon induction with IPTG and glucose. Effective fusion protein purification, refolding, auto-catalytic cleavage and mature EK recovery were described. The specific activity of the purified EK was determined as 110+/- 10 U/mg, which was comparable to a specific activity of > or =20 U/mg of the E. coli expressed EK sample provided by Sigma (Cat. No. E4906). This procedure produced approximately 53 mg of EK per 500 mL of cell culture, which was much higher than previous reports, thus providing a basis for large-scale production of EK and for further applications in biotechnology.

Tumor accumulation, degradation and pharmacokinetics of elastin-like polypeptides in nude mice

ELPs are genetically engineered, thermally responsive polypeptides that preferentially accumulate in solid tumors subjected to focused, mild hyperthermia. In this paper, we report the biodegradation, pharmacokinetics, tumor localization, and tumor spatial distribution of (14)C-labeled ELPs that were radiolabeled during their biosynthesis in Escheriehia coli. The in vitro degradation rate of a thermally responsive (14)C-labeled ELP1 ([(14)C] ELP1) with a molecular weight of 59.4 kDa, upon exposure to murine serum, was 2.49 wt.%/day. The apparent in vivo degradation rate of ELP1 after intravenous injection of nude mice was 2.46 wt.%/day and its terminal half-life was 8.7 h. The tumor accumulation and spatial distribution of intravenously administered ELP1 and a control ELP that was designed to remain soluble in heated tumors (ELP2) were examined in both heated (41.5 degrees C) and unheated tumors. ELP1 accumulated at a significantly higher concentration in heated tumors than ELP1 in unheated tumors and ELP2 in heated tumors. Quantitative autoradiography of tumor sections provided similar tumor accumulation results as the whole tumor analysis but, in addition, showed that ELP1 had a more homogeneous distribution in heated tumors and a greater concentration in the tumor center than either control treatment.