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Y Kim

Publications and source records attributed to Y Kim.

At least 721 records · Page 40Linked to original sources
PubMed1992

Genistein inhibits protein histidine kinase.

Protein histidine kinase was prepared from whole cell extracts of the yeast, Saccharomyces cerevisiae. The enzyme was assayed using either histone H4 or a synthetic peptide corresponding to residues 70 to 102 of histone H4 as an in vitro substrate. With either substrate, both genistein and its solvent, dimethyl sulfoxide (Me2SO), inhibited protein histidine kinase. Me2SO alone gave a cooperative dose-response curve, with inhibition changing from almost zero below 10% Me2SO to 80% at 20% Me2SO with either substrate. Genistein gave a simple dose-response curve with 50% inhibition of protein histidine kinase at 110 microM genistein. In experiments with protein histidine kinase, genistein was a noncompetitive inhibitor with respect to ATP, histone H4 or the synthetic peptide, although, in the case of the synthetic peptide, the data were also consistent with competitive inhibition. These data gave Km values for both ATP and histone H4 of 15 microM, in satisfactory agreement with previously reported values (Huang, J., Wei, Y., Kim, Y., Osterberg, L., and Matthews, H. R. (1991) J. Biol. Chem. 266, 9023-9031). The Km for the synthetic peptide was 80 microM. The KI values were 270 or 310 microM measured with histone H4 or the synthetic peptide as substrate, respectively. While these KI values are relatively high, relative to published KI values for genistein inhibition of protein tyrosine kinases, many reported experiments use genistein at concentrations where inhibition of protein histidine kinase occurs. It is possible that some of the observed effects of genistein in vivo may be due to inhibition of protein histidine kinase.

Adenosine Triphosphate↗
PubMed1992

pH dependent conformational changes in the T- and R-states of insulin in solution: circular dichroic studies in the pH range of 6 to 10.

Zinc insulin hexamer has been shown to undergo a phenol-induced T6 to R6 conformational transition in solution. Our circular dichroic (CD) studies demonstrate that insulin undergoes pH-dependent conformational changes over the pH range of 6-10 in the T-state and in the R- state. In order to determine which specific amino acid residues may be responsible for these pH-dependent changes, a series of insulin analogs were utilized. In the T-state, the pH dependent CD changes monitored in the far UV region have a pK of 8.2 and appear to be related to the titration of the A1-Gly amino group. Using the near UV CD a second pH-dependent conformational change was detected with a pK of 7.5 in the T-state. 1H N.M.R. studies suggest that B5-His may be responsible for this conformational transition. In the presence of m-cresol (R-state), the pK value was found to be 6.9. During this titration, the increased ellipticity for the R-state is diminishing as pH decreases from pH 8 to 6, and no difference in ellipticity was observed at 255 nm between T- and R-states at pH 6. Therefore, this may be due to the transition from the R back to the T-state.

Circular Dichroism↗
PubMed1992

Butylated hydroxytoluene prevents cumene hydroperoxide-induced Ca2+ release from liver mitochondria by inhibiting pyridine nucleotide hydrolysis.

The mechanism by which the free radical scavenger butylated hydroxytoluene (BHT) prevents cumene hydroperoxide-induced Ca2+ release from rat liver mitochondria was studied. In Ca(2+)-loaded mitochondria cumene hydroperoxide induced a rapid oxidation and subsequent hydrolysis of the pyridine nucleotides. In the presence of BHT, pyridine nucleotide oxidation by cumene hydroperoxide occurred but was reversible as hydrolysis was prevented by BHT. However, the addition of BHT directly to rat liver submitochondrial particles did not inhibit NAD+ hydrolysis or the formation of ADP-ribose from NAD+. Thus, whilst BHT prevented NAD+ hydrolysis in isolated mitochondria, this appeared not to be due to a direct effect of BHT on the NADase. It is concluded that the mechanism of action of BHT on cumene hydroperoxide-induced Ca2+ release from mitochondria involves the inhibition of pyridine nucleotide hydrolysis by an indirect mechanism rather than the radical scavenging properties of BHT.

Adenosine Diphosphate Ribose↗
PubMed1992

Definition of the catalytic site of cytochrome c oxidase: specific ligands of heme a and the heme a3-CuB center.

The three-subunit aa3-type cytochrome c oxidase (EC 1.9.3.1) of Rhodobacter sphaeroides is structurally and functionally homologous to the more complex mitochondrial oxidase. The largest subunit, subunit I, is highly conserved and predicted to contain 12 transmembrane segments that provide all the ligands for three of the four metal centers: heme a, heme a3, and CuB. A variety of spectroscopic techniques identify these ligands as histidines. We have used site-directed mutagenesis to change all the conserved histidines within subunit I of cytochrome c oxidase from Rb. sphaeroides. Analysis of the membrane-bound and purified mutant proteins by optical absorption and resonance Raman spectroscopy indicates that His-102 and His-421 are the ligands of heme a, while His-284, His-333, His-334, and His-419 ligate the heme a3-CuB center. To satisfy this ligation assignment, helices II, VI, VII, and X, which contain these histidine residues, must be in close proximity. These data provide empirical evidence regarding the three-dimensional protein structure at the catalytic core of cytochrome c oxidase.

Amino Acid Sequence↗
PubMed1992

Structure and evolution of four POU domain genes expressed in mouse brain.

Four mouse POU domain genomic DNA clones--Brain-1, Brain-2, Brain-4, and Scip--and Brain-2 cDNA, which are expressed in adult brain, were cloned and the coding and noncoding regions of the genes were sequenced. The amino acid sequences of the four POU domains are highly conserved; sequences in other regions of the proteins also are conserved but to a lesser extent. The absence of introns from the coding regions of the four POU domain genes and the similarity of amino acid sequences of the corresponding proteins suggest that the coding region of the ancestral class III POU domain gene lacked introns and therefore may have originated by reverse transcription of a molecule of POU domain mRNA followed by insertion of the cDNA into germ cell genomic DNA. Additional duplications of the ancestral class III POU domain gene (or mRNA) would create the Brain-1, Brain-2, Brain-4, and Scip genes.

Amino Acid Sequence↗
PubMed1992

Hox-1.11 and Hox-4.9 homeobox genes.

Mouse Hox-1.11 and Hox-4.9 genes were cloned, and the nucleotide sequences of the homeobox regions were determined. In addition, nucleotide sequence analysis of the homeobox regions of cloned Hox-4.3 and Hox-4.2 genomic DNA revealed some differences in nucleotide sequences and in the deduced homeodomain amino acid sequences compared with the sequences that have been reported.

Amino Acid Sequence↗
PubMed1992

Structure of a ricin mutant showing rescue of activity by a noncatalytic residue.

Ricin A chain is an N-glycosidase which removes a single adenine base from a conservative loop of 28S rRNA, thereby inactivating eukaryotic ribosomes. The mechanism of action has been proposed to include transition-state stabilization of an oxycarbonium ion on the substrate ribose by interaction with Glu 177. Conversion of Glu 177 to Gln reduces activity nearly 200-fold [Ready, M. P., Kim, Y., & Robertus, J. D. (1991) Proteins: Struct., Funct., Genet. 10, 270-278] while conversion to Ala (E177A) reduces activity only 20-fold [Schlossman, D., Withers, D., Welsh, P., Alexander, A., Robertus, J., & Frankel, A. (1989) Mol. Cell. Biol. 9, 5012-5021]. X-ray analysis of the latter mutant protein shows that a residue at the edge of the active site, Glu 208, rotates into the space left vacant by the mutation. Its rearranged carboxylate partially substitutes for that of Glu 177. This is equivalent to the rescue of enzyme activity by a second-site reversion. Kinetic analysis shows the E177A mutation affects kcat and not Km, consistent with the notion that the carboxylate serves in transition-state stabilization.

Amino Acid Sequence↗
PubMed1992

Molecular cloning and sequence of cDNA encoding the pyrophosphate-energized vacuolar membrane proton pump of Arabidopsis thaliana.

The energy-dependent transport of solutes across the vacuolar membrane (tonoplast) of plant cells is driven by two H+ pumps: a vacuolar ("V-type") H(+)-ATPase (EC 3.6.1.3) and a H(+)-translocating (pyrophosphate-energized) inorganic pyrophosphatase (H(+)-PPase; EC 3.6.1.1). The H(+)-PPase, like the V-type H(+)-ATPase, is abundant and ubiquitous in the vacuolar membranes of plant cells, and both enzymes make a substantial contribution to the transtonoplast H(+)-electrochemical potential difference. Here, we report the cloning and sequence of cDNAs encoding the tonoplast H(+)-PPase of Arabidopsis thaliana. The protein predicted from the nucleotide sequence of the cDNAs is constituted of 770 amino acids and has a molecular weight of 80,800. It is a highly hydrophobic integral membrane protein, and the structure derived from hydrophilicity plots contains at least 13 transmembrane spans. Since the tonoplast H(+)-PPase appears to be constituted of one polypeptide species and genomic Southern analyses indicate that the gene encoding the Mr 80,800 polypeptide is present in only a single copy in the genome of Arabidopsis, it is suggested that the H(+)-PPase has been cloned in its entirety. The lack of sequence identities between the tonoplast H(+)-PPase and any other characterized H+ pump or PPi-dependent enzyme implies a different evolutionary origin for this translocase.

Amino Acid Sequence↗
PubMed1992

Characterization of catechol 2,3-dioxygenases.

Three catechol 2,3-dioxygenases for biphenyl, naphthalene/salicylate, and toluene/xylene oxidation were cloned from Achromobacter xylosoxidans KF701, Pseudomonas putida (NAH7), and Pseudomonas sp. (pWWO). The cloned catechol 2,3-dioxygenases were identified by enzymatic activity assay in addition to yellow bands on polyacrylamide gel after electrophoresis and activity staining. All of the cloned catechol 2,3-dioxygenases exhibited their highest activities on catechol as a substrate compared with catechol derivatives including 4-chlorocatechol, 3-methylcatechol, and 4-methylcatechol. The cloned catechol 2,3-dioxygenases are not fused proteins but were significantly different from one another in their electrophoretic mobilities on nondenaturing 7.5%-polyacrylamide gel.

Alcaligenes↗
PubMed1992

The group I intron of apocytochrome b gene from Chlamydomonas smithii encodes a site-specific endonuclease.

The mitochondrial DNA molecules of two interfertile algal species, Chlamydomonas smithii and C. reinhardtii, are co-linear except for a 1075 bp intron (the alpha-insert) that is present in the cob gene of C. smithii. The alpha-insert, a group I intron (Cs cob.1) containing an open reading frame (ORF) which encodes a basic, hydrophilic protein of 237 amino acids, is unidirectionally transmitted to all diploid progeny during interspecific crosses. In this report, we show that the Cs cob.1-encoded protein is a site-specific endonuclease (I-Csm I) which could mediate the intron transfer via the gene conversion mechanism. The Cs cob.1 ORF was cloned into the vector pMALcr1 and over-expressed as a hybrid protein fused to maltose-binding protein (MBP). This fusion protein exhibited an in vivo endonuclease activity which specifically cleaved the intron homing site within the intronless cob gene.

Algal Proteins↗
PubMed1992

Primary cultures of middle ear epithelial cells from chinchillas.

A reproducible method is presented for primary cultures of middle ear epithelial cells (MEEC) from chinchillas. The MEEC were first dissociated with protease and grown on collagen-coated membrane using a culture medium containing equal volumes of Dulbecco's modified Eagle medium and Ham's F12 supplemented with 0.5% fetal bovine serum. Outgrowth of cells was first noted within 24 h, reaching confluency in 6-7 days. These cells grew in a monolayer and appeared to be ovoid or polygonal. By immunofluorescence microscopy, these cells stained for cytokeratin, but not for type III collagen. In contrast, fibroblasts stained for type III collagen, but not for cytokeratin. Based on growth characteristics, morphology, and immunofluorescent findings, these cells were determined to be epithelial cells. To retard the outgrowth of fibroblasts, 5 mM putrescine was added to the culture medium on the 2nd day of explant. Contamination with fibroblasts was consistently less than 5% when defined as type III collagen-positive cells. Establishment of a method for the primary culture of MEEC will provide a new approach for studying the role of epithelial cells in the pathogenesis of various types of otitis media.

Animals↗
PubMed1992

Pollen-specific expression of the Arabidopsis thaliana alpha 1-tubulin promoter assayed by beta-glucuronidase, chloramphenicol acetyltransferase and diphtheria toxin reporter genes.

We have characterized the promoter specificity of the Arabidopsis thaliana alpha 1-tubulin (alpha 1-tub) gene by studying expression patterns of gene fusions between the 2.2 kbp 5' upstream region of the alpha 1-tub gene and each of three different reporters: chloramphenical acetyltransferase, beta-glucuronidase or the diphtheria toxin chain A gene. Analysis of transgenic tobacco and Arabidopsis plants carrying the transgene showed that the chloramphenicol acetyltransferase and beta-glucuronidase activities were not detected in any vegetative or reproductive organs except mature pollen. Transgenic tobacco plants carrying the diphtheria toxin chain A gene under the control of the alpha 1-tub promoter were of normal phenotype but seed fertility was drastically reduced. Furthermore, the transgene could not be transmitted to the next generation through pollen, supporting the observation that the alpha 1-tub promoter is active only in pollen. It was observed that the promoter activity was most active in mature pollen and decreased significantly during in vitro pollen germination, indicating that the promoter is inactive or subdued in germinating pollen. The promoter activity was not affected by various plant growth hormones during pollen maturation.

Arabidopsis↗
PubMed1992

Hardware and software requirements for a picture archiving and communication system's diagnostic workstations.

Electronic systems (picture archiving and communications systems [PACS]) for image and multimedia data distribution, archiving, and transmission, represent the future of radiology. The workstation is the point of contact between a PACS and the radiologist or referring physician. Therefore, the acceptance of PACS is highly dependent on workstation functionality and performance. This paper, based on our experience in evaluating commercial workstations and on a review of recent literature, describes hardware and software requirements for diagnostic workstations that could be used for making primary diagnoses in a radiology department. Requirements for PACS workstations for use in referring clinics are also briefly described. These workstations must be able to handle the large volume of images to be viewed efficiently, add new functionality to improve the productivity of physicians, technologists, and other health care providers, and provide enough flexibility to allow the electronic systems to grow as medical imaging technology evolves.

Computer Systems↗
PubMed1992

Role of antibodies to tubulointerstitial nephritis antigen in human anti-tubular basement membrane nephritis associated with membranous nephropathy.

We report three patients, from two unrelated families, with anti-tubular basement membrane (TBM) antibody nephritis associated with membranous nephropathy. This rare disorder is characterized by nephrotic syndrome, tubular dysfunction, and progression to renal failure. Direct immunofluorescent studies in these patients revealed linear IgG deposition along the proximal TBM, while circulating antibodies reacting with proximal TBM but not with glomerular basement membrane were identified by indirect immunofluorescence. Sera from all three patients reacted by enzyme-linked immunosorbent assay and Western immunoblotting with purified 58-kd tubulointerstitial nephritis (TIN) antigen isolated from TBM. Additional reactivity with a 175-kd component, which may be a higher-molecular-weight form of TIN antigen, was observed by immunoblotting. Since recurrent Fanconi syndrome was seen after transplantation in one patient, anti-TBM antibodies were removed by plasmapheresis prior to kidney transplantation in the other two patients. Neither patient has clinical evidence of recurrent anti-TBM nephritis in the allograft despite the posttransplantation reappearance of anti-TBM antibodies in the serum of one patient. Serologic and molecular HLA class I and class II polymorphism analysis has identified the presence of both HLA-B7 and -DRw8 antigens in two unrelated affected individuals (0.3% expected frequency in the white population). We conclude that sera from patients with anti-TBM nephritis associated with membranous nephropathy react with 58-kd TIN antigen previously implicated in the pathogenesis of primary anti-TBM nephritis. This rare autoimmune disorder may be HLA associated with B7 and/or DRw8, providing susceptibility to the disease. Further investigation is needed to understand the pathogenesis of recurrent anti-TBM nephritis in the renal allograft.

Antibodies, Anti-Idiotypic↗