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Biomedical subjects

S I Kim

Publications and source records attributed to S I Kim.

At least 109 records · Page 6Linked to original sources
PubMed1998

Major identity element of glutamine tRNAs from Bacillus subtilis and Escherichia coli in the reaction with B. subtilis glutamyl-tRNA synthetase.

Early investigations revealed that Bacillus subtilis glutamyl-tRNA synthetase [GluRS (bs)] is responsible for aminoacylating both glutamate tRNA [tRNA(Glu) (bs)] and glutamine tRNA [tRNA(Gln) (bs)] with glutamate. The same Bacillus enzyme can also efficiently attach glutamate to one isoacceptor glutamine tRNA [tRNA(Gln) (ec)] of Escherichia coli in vitro but not to tRNA2(Gln) (ec) and tRNA(Glu) (ec). To characterize identity elements of these glutamine tRNAs in the interaction with GluRS (bs), tRNA2(Gln) (ec), tRNA1(Gln) (ec), three other mutant glutamine tRNAs [tRNA2(Gln) (AU) (C34 --> U34), tRNA2(Gln) (12M) (C34 --> U34, 31A-U39 --> 31U-A39), and tRNA2(Gln) (M21) (64C --> G50 --> 64G-C50, 63U-A51 --> 63A-U51)] originated from tRNA2(Gln) (ec), tRNA(Gln) (bs), and a mutant tRNAM(Gln) (bs) whose U at the 34th position (U34), was replaced to C (C34), were produced in E. coli. All of the E. coli glutamine tRNAs containing U34 such as tRNA1(Gln), tRNA2(Gln) (AU), and tRNA2(Gln) (12M) could be charged with glutamate by GluRS (bs), whereas tRNA2(Gln) (ec) and its T-stem mutant tRNA2(Gln) (M21) containing C34 could not be charged by the same enzyme. The unique change of C34 to U34 of tRNA2(Gln) (ec) acquired glutamate acceptor activity by GluRS (bs). This result suggests that the U34 is the major identity element of tRNA1(Gln) (ec) in the recognition by GluRS (bs). The same situation was found in tRNA(Gln) (bs). The glutamate acceptor activity of tRNA(Gln) (bs) disappeared on replacement of U34 to C34. To find out whether modified bases in tRNA(Gln) (bs) are involved in the recognition by GluRS (bs), glutamylation of tRNA(Gln) (bs) produced by in vitro transcription was also examined but the in vitro transcript of tRNA(Gln) (bs) could not be charged with glutamic acid by GluRS (bs). All of these mean that the major recognition element for GluRS (bs) is U at the 34th position of both tRNA(Gln) (bs) and tRNA1(Gln) (ec) as a modified form.

Amino Acyl-tRNA Synthetases↗
PubMed1998

Organization and transcriptional characterization of the cat1 gene cluster in Acinetobacter lwoffi K24.

Previously, we have reported that two clustered cat genes from Acenitobacter lwoffi K24 had different arrangements, catB1C1A1 and catB2A2C2 (Kim, S.I., S.-H. Leem, J.-S. Choi, Y.H. Chung, S. Kim, Y.-M. Park, Y.K. Park, Y.N. Lee, and K.-S. Ha. 1997, J. Bacteriol. 179, 5226-5231). By further analysis of the organization of the cat1 gene cluster, we obtained a complete sequence of the catB1 gene, which encoded 40.8-kDa polypeptide containing 379 amino acids, and found a open reading frame (ORF) coding a putative regulatory protein in upstream region of catB1 on plasmid pCD1-1. This ORF encoded 34.2-kDa polypeptide containing 379 amino acids and had more than 40% identity with catR, LysR family regulatory protein of Pseudomonas putida. RT-PCR, Northern blot analysis and primer extension assay for transcriptional analysis of the cat1 gene cluster revealed that the catB1C1 genes were cotranscribed and the catA1 gene was independently transcribed.

Acinetobacter↗
PubMed1998

Enzymatic phosphorylation of food proteins by purified and recombinant protein kinase CK2.

Protein kinase CK2 formerly called casein kinase II is a protein kinase able to phosphorylate more than 100 proteic substrates. We have purified protein kinase CK2 from the yeast Y. lipolytica to phosphorylate milk and plant reserve proteins to a significant extent. In the case of plant reserve proteins, which are polymeric substrates, not all subunits are substrate for protein kinase CK2, even if non phosphorylated subunits contain significant potent phosphorylations sites. Best substrates were soy beta-conglycinin (0.72 P/mol) and dephosphorylated caseins (0.5 P/mol). We have studied some functional properties of phosphorylated caseins. Solubility was improved for all pH values but pI. Sensitivity to calcium has also been assessed, and it is slightly improved upon phosphorylation. We have cloned the catalytic subunit of protein kinase CK2 from yeast Y. lipolytica. The recombinant catalytic subunit expressed in E. coli was active and displayed kinetic properties similar to those of the purified enzyme. The recombinant catalytic subunit was able to phosphorylate plant reserve proteins and milk proteins to a significant extent. Best substrates were soy beta-conglycinin (1.0 P/mol), and glycinin (0.59 P/mol).

Calcium↗
PubMed1998

Expression and characterization of the recombinant catalytic subunit of casein kinase II from the yeast Yarrowia lipolytica in Escherichia coli.

The alpha catalytic subunit of casein kinase II from the yeast Yarrowia lipolytica has been cloned and overexpressed using the pT7-7 expression vector in Escherichia coli. Casein kinase activity is found in the bacterial extracts. The catalytic subunit is partially expressed in a soluble and active form, which is purified to electrophoretic homogeneity. Most of the enzyme was found in inclusion bodies. In this form, the enzyme, which is almost pure, exhibits a low specific activity. We have focused our efforts on methods to activate the protein from the inclusion bodies. We have studied the renaturation of urea-denaturated CKII catalytic subunit. We have tried different renaturation buffers and found that renaturation by dilution was more efficient than renaturation by dialysis. Treatment of the enzyme found in the inclusion bodies with different nondetergent sulfobetaines (NDSB) led to a time-dependent activation. NDSB195 is a V-type activator of the recombinant catalytic subunit of casein kinase II. The NDSB195-activated enzyme remained active at the room temperature for weeks. Kinetic properties of the recombinant casein kinase II subunit are similar to those of the purified holoenzyme (low Km for ATP and inhibition by heparin). Kinetic study indicates that the beta subunit could interact with the alpha subunit at the level of the catalytic site to enhance activity and to modify the kinetic behavior of the enzyme.

Base Sequence↗
PubMed1998

Anticomplementary activity of ginseng saponins and their degradation products.

The anticomplementary activity of ginseng saponins and their degradation products obtained by chemical treatment of Korean red ginseng saponins was investigated. The total saponin and its major components showed strong anticomplementary activity and their structure-activity relationship was evaluated.

Complement Inactivator Proteins↗
PubMed1998

Purification and some properties of IMP dehydrogenase of Bacillus cereus.

IMP dehydrogenase was purified from a crude extract of B, cereus cells. The molecular mass of the purified enzyme was estimated to be 56 kDa by SDS-PAGE and 225 kDa by gel filtration. The optimum pH of the enzyme was about 9.5. The first seven residues at N-terminus of the enzyme was determined to be Met-Trp-Glu-Ser-Lys-Phe-Val. The enzyme showed a significant specificity for inosine nucleotides among 15 purines and pyrimidines tested, but not acted on other purines and pyrimidines including inosine. Among 11 metal ions and 3 enzyme inhibitors tested, Al3+ activated the IMP dehydrogenase. The enzyme activity was strongly inhibited by Zn2+ and Fe3+.

Ammonium Sulfate↗
PubMed1998

Involvement of glucocorticoid receptor in the induction of differentiation by ginsenosides in F9 teratocarcinoma cells.

We have previously reported that ginsenosides Rh1 and Rh2 induced the differentiation of F9 teratocarcinoma stem cells [Lee, Y. N., Lee, H. Y., Chung, H. Y., Kim, S. I., Lee, S. K., Park, B. C. and Kim, K. W., In vitro induction of differentiation by ginsenosides in F9 teratocarcinoma cells. Eur. J. Cancer 1996, 32, 1420-1428.]. Since the chemical structure of Rh1 and Rh2 is very similar to that of dexamethasone, a synthetic glucocorticoid, we investigated whether Rh1 and Rh2 act through the glucocorticoid receptor (GR). Immunocytochemistry showed that Rh1 or Rh2 increased the nuclear translocation of GR in the same manner of dexamethasone. In the gel shift assay, glucocorticoid response element (GRE) binding protein in F9 cells was increased by Rh1 or Rh2. To confirm whether the increased binding protein is GR, we performed the competition assay with unlabeled GRE as a specific competitor. Moreover, supershift assay with the GR antibody showed that the binding proteins are GR. In addition, to confirm the Rh1 or Rh2-induced transactivation of GRE promoter, we cotransfected GR expression vector and GRE-luciferase vector. In the luciferase assay, Rh1 or Rh2 potently induced luciferase activity and this induction was blocked by RU486, a potent GR antagonist. Taken together, we suggest that ginsenosides Rh1 and Rh2 may induce the differentiation of F9 cells by stimulating the nuclear translocation of GR.

Animals↗