Production of recombinant human pancreatic secretory trypsin inhibitor by Escherichia coli

Biochemistry and biology of SPINK-PSTI and monitor peptide

This article summarizes structural and functional properties of pancreatic secretory trypsin inhibitor (PSTI), which has been identified in many species. Its prominent role is to protect the pancreas from prematurely activated trypsinogen before entry into the duodenum. In the rat there are two isoforms, one of which is PSTI-I, a 61-amino acid peptide involved in the feedback regulation of pancreatic enzymes. Independent investigations in neoplastic diseases led to the discovery of tumor-associated trypsin inhibitor,which is identical to PSTI.

Detection of human T cell receptor cDNAs (alpha, beta, gamma and delta) by ligation of a universal adaptor to variable region

The study of T cell receptor (TCR) genes has been hampered by their large repertoires and elusive methods for gene amplification. We have developed a new method for amplification of all human TCR genes (alpha, beta, gamma, and delta) with the ligation of a universal adaptor to the leader sequence of variable (V) regions, which permitted effective and reproducible amplification of all four types of TCR genes. cDNA sequencing of TCR-gamma, -delta, -alpha, -beta was carried out in respectively 15, 13, 28, and 26 T cell clones from human peripheral blood T cells using a newly developed universal adaptor and these methods. TCR-gamma V-II (V gamma 9) was a major population, and V-I (V gamma 2 and 3) and V-III (V gamma 10) were next major populations among TCR-gamma subfamilies, and confirmed the previous observations determined using mAbs specific to TCR-gamma. All five clones of TCR-gamma V-II and three of five clones of TCR-gamma V-I subfamilies had in-frame V-N-J junctions. In contrast, sequences from both TCR-gamma V-III (4/4 clones) and V-IV (1/1 clones) subfamilies had intron-like regions that caused out-of-frame cDNA, suggesting that most of TCR-gamma V-III and V-IV in PBL are not functional. V delta 2 was a major population and V delta 1 was a next predominant population among TCR-delta subfamilies, also confirming the previous observations determined using mAbs to TCR-delta. With regards to TCR-alpha and -beta, this new method randomly amplified TCR cDNAs. In addition, the sequences of 5' portions of three TCR-V-alpha and one TCR-V beta were extended. Two new TCR-alpha subfamilies and one new TCR-beta family were also identified. In summary, this new method will provide a scientific tool for understanding structures of the human TCR genes involved in specific immune responses.

Expression and excretion of human pancreatic secretory trypsin inhibitor in lipoprotein-deletion mutant of Escherichia coli

We constructed a gene coding for the 56-amino acid human pancreatic secretory trypsin inhibitor (PSTI), and ligated it on a plasmid downstream from the trp promoter and the signal peptide sequence of alkaline phosphatase. The resulting plasmid was transfected into a lipoprotein deletion mutant (Escherichia coli JE5505) and the plasmid-carrying cells were induced with 3-indoleacrylic acid. A considerable amount (50 micrograms/ml culture) of the mature PSTI protein was detected in the culture supernatant. The excreted PSTI was identical to the natural PSTI protein with respect to the trypsin-inhibiting activity, the N-terminal and the C-terminal amino acid sequences and the amino acid composition.

Insulin resistance by unprocessed insulin proreceptors point mutation at the cleavage site

Failure to cleave the interconnecting site between alpha- and beta-subunit produced insulin proreceptors in the plasma membranes which had markedly low affinity to insulin, leading to extreme insulin resistance in a patient. We performed cDNA sequence analysis of the cleavage site of the insulin proreceptor from the patient. Polymerase chain reaction was used to obtain large amount of cDNA coding for the region including the interconnecting site. A thermostable DNA polymerase, Taq polymerase, successfully produced enough amount of cDNA of the region to be sequenced. The results showed AGG (Arg) to AGT (Ser) point mutation, resulting in the change of interconnecting sequence of the two subunits from -Arg-Lys-Arg-Arg- to -Arg-Lys-Arg-Ser-. These results suggest that the tertial structure change of the cleavage site leads to production of unprocessed insulin proreceptors.