DNA sequencing of the gene encoding Salmonella typhimurium-derived T-cell inhibitor (STI) and characterization of the gene product, cloned STI.
In a previous study, we found a novel protein which inhibited T-cell responsiveness to interleukin-2 (IL-2) in Salmonella typhimurium and called it S. typhimurium-derived T-cell inhibitor (STI). In this study, we analyzed the DNA sequence of the gene encoding STI. The STI gene was cloned into a plasmid vector, pUC118, and expressed in Escherichia coli JM109. Like native STI, the cloned STI inhibited IL-2-dependent CTLL-2 cell growth. Furthermore, this growth inhibition involved down-regulation of IL-2 receptor expression. These results indicate that the cloned STI expressed in E. coli was identical to native STI. Sequencing revealed that the STI gene contained an open reading frame of 2298 base pairs encoding a precursor form of 765 amino acid residues (molecular mass 83605) that is processed into a mature form of 745 amino acid residues with molecular mass 81 548. Homology analysis revealed that its amino acid sequence was highly homologous with that of the beta-glucosidase of E. coli K-12. We designated the gene encoding STI sti.
Matsui
K
K
Department of Microbiology, Meiji College of Pharmacy, Tokyo, Japan.
Nagano
K
K
Arai
T
T
Hirono
I
I
Aoki
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004926:Escherichia coli; D015870:Gene Expression; D005798:Genes, Bacterial; D051379:Mice; D008969:Molecular Sequence Data; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D015375:Receptors, Interleukin-2; C118240:T-cell inhibitor, STI protein, Salmonella typhimurium