Kikuchi Masakazu

Expression of hepatitis B virus surface antigen P31 gene in Escherichia coli

A hepatitis B virus surface antigen (HBsAg) P31-coding DNA was constructed from a DNA fragment of the plasmid pHBr330 containing the entire hepatitis B virus (HBV) adr DNA and a chemically synthesized adaptor. The P31 gene was inserted into an expression vector, pTRP771, having an Escherichia coli tryptophan operon (trp) promoter to give a recombinant plasmid pTRP P31-R. The distance between the Shine-Dalgarno (SD) sequence and the initiation codon of P31 gene was adjusted to 9 bp. The expression level of HBsAg by E. coli 294[pTRP P31-R] was significantly elevated, in contrast to that of HBsAg by E. coli 294[pTRP SS-6]. Western blotting analysis has shown that E. coli[pTRP P31-R] synthesizes a specific polypeptide P31 of about 31 kDal, which reacts with anti-HBsAg antibody. The binding studies with polyalbumins from various species have also suggested that HBsAg P31 specifically binds to polymerized human serum albumin.

Expression of human lysozyme in an insoluble form in yeast

Abstract A high level of expression in yeast of a chemically synthesized human lysozyme (hL) gene was achieved by introducing an A-rich DNA fragment just upstream from the ATG start codon. The synthesized recombinant human lysozyme (r-hL) was insoluble and biologically inactive. It was solubilized with 7 M urea (pH 9) from yeast cells and its lytic activity was efficiently regenerated by oxidative renaturation. This rknaturation experiment and Western blotting analysis under reducing and non-reducing conditions indicate that the insoluble form might be caused by the formation of incorrect intra- or intermolecular disulfide bonds. The N-terminal amino acid sequence of the purified r-hL was identical with that of authentic hL.

High-level secretion of the extracellular domain of the human growth hormone receptor using a baculovirus system

Abstract A chemically synthesized gene (hGHR-ED) coding for the extracellular domain (ED) of the human growth hormone (hGH) receptor (hGHR) was inserted into the genome of Autographa californica nuclear polyhedrosis virus adjacent to the polyhedrin promoter. Spodoptera frugiperda cells infected with the recombinant virus secreted a protein with hGH-binding activity into the medium. The secreted 35-kDa protein was purified to near homogeneity. The purified protein exhibited a high binding affinity ( K d = 0.2—0.3 nM ) to hGH. The highest cell production capability was estimated at more than 10–20 μg hGHR-ED/ml of culture. The inhibition of the hGHR-ED secretion by treatment with tunicamycin suggests that glycosylation is important for secretion.