Studying the expression of a lipase from Pyrococcus furiosus using response surfaces

Expression, purification, and characterization of asparaginase II from Saccharomyces cerevisiae in Escherichia coli

l-asparaginase catalyzes the conversion of l-asparagine to l-aspartate and ammonium. This protein is an important therapeutic enzyme used for the treatment of acute lymphoblastic leukemia. In this study, the asparaginase II-encoding gene ASP3 from Saccharomyces cerevisiae was cloned into the expression vector pET28a in-fusion with a 6x histidine tag and was expressed in Escherichia coli BL21 (DE3) cells. The protein was expressed at a high level (225.6 IU/g cells) as an intracellular and soluble molecule and was purified from the supernatant by nickel affinity chromatography. The enzyme showed very low activity against l-glutamine. The denaturing electrophoresis analysis indicated that the recombinant protein had a molecular mass of ∼38 kDa. The native enzyme was a tetramer with a molecular mass of approximately 178 kDa. The enzyme preparation showed antitumor activity against the K562 and Jurkat cell lines comparable or even superior to the E. coli commercial asparaginase.

Expression and purification of the extracellular domain of the human follicle-stimulating hormone receptor using Escherichia coli

AIM

Although much is known about the structure and biological functions of follicle-stimulating hormone (FSH) receptor (FSHR), the interaction of FSHR and FSH has been challenging to characterize due to the limited quantity of active FSHR protein produced by simple methods. The goal of this study was to express and purify the extracellular domain (ECD) of human FSHR (hFSHR).

METHODS

Total RNA was isolated from normal human ovary tissue. cDNA for hFSHR ECD were amplified and subsequently ligated into the pET32a(+) vector. The plasmid vector construct was confirmed by polymerase chain reaction and sequencing. Expression in Escherichia coli Rosetta (DE3) pLysS strain was induced by isopropyl-thio-β-D-thiogalactoside, and the recombinant products were purified by immuno-affinity chromatography using an Ni-NTA and High-Q column. The recombinant protein was confirmed by western blotting.

RESULTS

Following induction, E. coli expressed a recombinant protein of approximately 65 kDa in size, whereas the non-induced E. coli did not express the recombinant protein. The recombinant fragments purified using a High-Q column demonstrated a single band and an abundant yield. The recombinant protein was soluble and specifically recognized by an antibody for hFSHR. Additionally, four mutation sites were detected that resulted in amino acid shifts at position 112 Asn/Thr, 197 Glu/Ala, 198 Leu/Val and 307 Ala/Thr.

CONCLUSION

The recombinant hFSHR ECD protein was expressed and purified. This method could be easily scaled for increased production and may facilitate additional applications utilizing FSHR in assisted reproductive technology, a contraceptive FSH vaccine and FSHR-targeted therapeutic agents used to treat ovarian cancer.