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J Kim

Publications and source records attributed to J Kim.

At least 991 records · Page 55Linked to original sources
PubMed1993

X-ray crystal structure of the nitrogenase molybdenum-iron protein from Clostridium pasteurianum at 3.0-A resolution.

The crystal structure of the nitrogenase molybdenum-iron (MoFe) protein from Clostridium pasteurianum (Cp1) has been determined at 3.0-A resolution by a combination of isomorphous replacement, molecular replacement, and noncrystallographic symmetry averaging. The structure of Cp1, including the two types of metal centers associated with the protein (the FeMo-cofactor and the P-cluster pair), is similar to that previously described for the MoFe-protein from Azotobacter vinelandii (Av1). Unique features of the Cp1 structure arise from the presence of an approximately 50-residue insertion in the alpha subunit and an approximately 50-residue deletion in the beta subunit. As a consequence, the FeMo-cofactor is more buried in Cp1 than in Av1, since the insertion is located on the surface above the FeMo-cofactor. The location of this insertion near the putative nitrogenase iron protein binding site provides a structural basis for the observation that the nitrogenase proteins from C. pasteurianum have low activity with complementary nitrogenase proteins isolated from other organisms. Mechanistic implications of the Cp1 structure for substrate entry/product release, substrate binding to the FeMo-cofactor, and electron- and proton-transfer reactions of nitrogenase are discussed.

Binding Sites↗
PubMed1993

Excimer laser keratectomy after radial keratotomy.

Radial keratotomy to treat myopia has been characterized by a lack of predictability. Until recently, patients with undercorrected myopia who were unsatisfied with their visual outcome could only be offered secondary augmentation procedures, which were equally unpredictable. We performed excimer laser keratectomy in six eyes of five patients whose myopia was undercorrected after radial keratotomy. The average residual spherical equivalent refractive error after radial keratotomy was -2.40 diopters, and this was reduced to -0.48 diopters after laser treatment. Final uncorrected visual acuity ranged from 20/80 to 20/20, and visual acuity was corrected to within one line of the preoperative best-corrected value in all patients. Epithelialization of all eyes occurred within four to six days. There were no incidences of corneal neovascularization, including no vascularization of the radial keratotomy incisions. Our findings suggest excimer phototherapeutic keratectomy offers a safe and more controlled method of augmenting undercorrected myopia after radial keratotomy.

Adult↗
PubMed1993

Adaptability at the protein-DNA interface is an important aspect of sequence recognition by bZIP proteins.

The related AP-1 and ATF/CREB families of transcriptional regulatory proteins bind as dimers to overlapping or adjacent DNA half-sites by using a bZIP structural motif. Using genetic selections, we isolated derivatives of yeast GCN4 that affect DNA-binding specificity at particular positions of the AP-1 target sequence. In general, altered DNA-binding specificity results from the substitution of larger hydrophobic amino acids for GCN4 residues that contact base pairs. However, in several cases, DNA binding by the mutant proteins cannot be simply explained in terms of the GCN4-AP-1 structure; movement of the protein and/or DNA structural changes are required to accommodate the amino acid substitutions. The quintet of GCN4 residues that make base-pair contacts do not entirely determine DNA-binding specificity because these residues are highly conserved in the bZIP family, yet many of the bZIP proteins bind to distinct DNA sites. The alpha-helical fork between the GCN4 DNA-binding and dimerization surfaces is important for half-site spacing preferences, because mutations in the fork alter the relative affinity for AP-1 and ATF/CREB sites. The basic region in the protein-DNA complex is a long isolated alpha-helix, with no constraints from other parts of a folded domain. From all of these considerations, we suggest that small shifts in position and orientation or local deformations in the alpha-helical backbone distinguish one bZIP complex from another.

Arginine↗
PubMed1993

The nitrogenase FeMo-cofactor and P-cluster pair: 2.2 A resolution structures.

Structures recently proposed for the FeMo-cofactor and P-cluster pair of the nitrogenase molybdenum-iron (MoFe)-protein from Azotobacter vinelandii have been crystallographically verified at 2.2 angstrom resolution. Significantly, no hexacoordinate sulfur atoms are observed in either type of metal center. Consequently, the six bridged iron atoms in the FeMo-cofactor are trigonally coordinated by nonprotein ligands, although there may be some iron-iron bonding interactions that could provide a fourth coordination interaction for these sites. Two of the cluster sulfurs in the P-cluster pair are very close together (approximately 2.1 angstroms), indicating that they form a disulfide bond. These findings indicate that a cavity exists in the interior of the FeMo-cofactor that could be involved in substrate binding and suggest that redox reactions at the P-cluster pair may be linked to transitions of two cluster-bound sulfurs between disulfide and sulfide oxidation states.

Azotobacter vinelandii↗
PubMed1993

Discordant p53 gene mutations in primary head and neck cancers and corresponding second primary cancers of the upper aerodigestive tract.

Patients with primary head and neck malignancies have a 3-7% yearly incidence of second primary cancers. It is thought that these second primary cancers arise independently following exposure to a common carcinogen by a process that has been called field cancerization. Since mutations in the p53 tumor suppressor gene represent a genetic alteration occurring during the evolution of premalignant lesions to malignancies of the upper aerodigestive tract, we analyzed mutations in the p53 gene of patients with cancer of the head and neck who developed second primary tumors of the upper aerodigestive tract epithelium to test the field cancerization hypothesis. DNA was extracted from primary head and neck cancers and second primary cancers of 31 patients. DNA from exons 5-8 of the p53 gene was analyzed by the single strand conformation polymorphism technique to identify the locations of the mutations in different regions of the gene. DNA from 6 patients was also sequenced by the chain termination method to confirm the presence of mutations and determine the base substitutions. Twenty-one of the 31 patients had 1 or more p53 mutations. In all 21 cases the genetic lesions were discordant such that the presence or location of the mutations in the initial primary cancer differed from those of the second and third primary cancers. In each of the five patients with mutations in both primary tumors, the mutations occurred in different regions of the p53 gene. Of the other 16 patients, 8 had a p53 mutation in the first primary but not the subsequent primary cancer and the other 8 had no mutation in the initial primary but did have a mutation in subsequent primary cancers. Sequencing confirmed the single strand conformation polymorphism analysis and showed that 73% of the mutations were transitions. The discordant p53 mutations in second primary cancers arising in patients with primary epithelial cancer of the upper aerodigestive tract suggest that these cancers arise as independent events. These observations provide the first demonstration of a molecular basis for field cancerization effects in cancers of the upper aerodigestive tract.

Adult↗
PubMed1993

Pivotal role of amino acid at position 138 in the allosteric hinge reorientation of cAMP receptor protein.

The cAMP receptor protein (CRP) of Escherichia coli needs cAMP for an allosteric change to regulate gene expression by binding to specific DNA sites. The hinge region connecting the DNA-binding domain to the cAMP-binding domain has been proposed to participate in the cAMP-induced allosteric change necessary to adjust C and D alpha-helices for movement of the DNA-binding F alpha-helix away from the protein surface. The role of the hinge region for a conformation change in CRP was tested by studying the effects of single amino acid substitutions at residue 138 located within the hinge. Physiological studies of wild-type and mutant cells and biochemical analysis of purified wild-type and mutant CRP revealed at least three groups of altered CRPs: (i) CRP that behaves like wild type (CRP+); (ii) CRP that binds cAMP but does not complete the structural changes required for specific DNA binding, proteolytic cleavage, and transcription activation (CRPallo); and (iii) CRP that shows some or all of these conformational changes without cAMP (CRP*). These results show a pivotal role of position 138 from which change emanates and provide further evidence that a hinge reorientation involving residue 138 is involved in the interhelical adjustments.

Allosteric Site↗
PubMed1993

Distribution and morphology of motoneurons innervating different muscle fiber types in an amphibian muscle complex.

The distribution and morphology of motoneurons innervating specific types of muscle fibers in the levator scapulae superior (LSS) muscle complex of the bullfrog (Rana catesbeiana) and tiger salamander (Ambystoma tigrinum) were studied by retrograde labelling with cholera toxin-conjugated horseradish peroxidase (CT-HRP). The LSS muscle complex in both of these amphibians has a segregated pattern of muscle-fiber types (tonic; fast oxidative-glycolytic twitch [FOG]; fast glycolytic twitch [FG]) along an anteroposterior axis. The entire motor pool was labelled by injection of CT-HRP into the whole LSS muscle complex. The motoneurons innervating specific fiber types were labelled by injection of CT-HRP into certain muscle regions. The organization of the motoneuron pool of the LSS complex of both species was arranged in two columns--one ventrolateral and one medial. In bullfrogs, the ventrolateral column contains motoneurons innervating FG and tonic fiber types and the medial column contains motoneurons innervating FOG fiber types. In tiger salamanders, the ventrolateral column contains motoneurons innervating FG fiber types and the medial column contains motoneurons innervating FOG and tonic fiber types. The different motoneuron types also have different soma sizes and patterns of dendritic arborization. In both species, FG motoneurons are the largest, whereas FOG motoneurons are intermediate in size and tonic motoneurons are the smallest. In bullfrogs, the main dendrites of FG motoneurons extend into the dorsolateral and the ventrolateral gray matter of the spinal cord, whereas the dendrites of FOG motoneurons extend into the ventral and medial cord. In the tiger salamander, dendrites of FG motoneurons extend into the ventrolateral spinal cord and dendrites of the FOG motoneurons extend more generally into the ventral cord. Dendrites of tonic motoneurons in both amphibians were small and short, and difficult to observe. These results establish that motoneurons innervating different types of muscle fibers in the LSS muscle complex are segregated spatially and display consistent morphological differences.

Ambystoma↗
PubMed1993

Determination of monosaccharides in glycoproteins by reverse-phase high-performance liquid chromatography.

This report examines monosaccharide composition and content using the reverse-phase high-performance liquid chromatographic separation of p-aminobenzoic ethyl ester derivatives of neutral and amino sugars released from glycoproteins. After acid hydrolysis of glycoproteins with 2 M trifluoroacetic acid, sugars are derivatized with p-aminobenzoic ethyl ester (ABEE), which strongly absorbs uv light at 254 nm in the presence of sodium cyanoborohydride. Reverse-phase (RP)-HPLC of the ABEE-sugar derivatives is performed on Pico.Tag column in an isocratic mode. RP-HPLC conditions are optimized by using ternary mixture as a mobile phase and 45 degrees C as a column temperature. This procedure is very useful for the simultaneous analysis of neutral and amino sugars in a single chromatographic step using RP-HPLC without reacetylation of deacetylated amino sugars, which were produced by acid hydrolysis, and additional chromatography to remove side products. Monosaccharide composition and contents determined on glycoproteins by this method were very comparable to those previously obtained by other techniques.

4-Aminobenzoic Acid↗
PubMed1993

Intracellular transport and virion incorporation of vpx requires interaction with other virus type-specific components.

Viral protein X (vpx) is a virion-associated HIV-2/SIV accessory protein that enhances viral infectivity and replication in natural target cells. To investigate whether other viral components affect its biosynthesis, subcellular localization, and virion incorporation, we expressed HIV-2 vpx in a mammalian cell system and examined its transport and packaging requirements using an in trans complementation assay. The complete vpx coding region of HIV-2ST was placed under the control of a high-efficiency promoter system (SR alpha) which contained both an SV40 promoter/enhancer region and R/U5 elements of the HTLV-1 LTR. Following transfection of Cos-1 cells, this construct (pSR alpha-vpx) facilitated high level expression of vpx, as demonstrated by Western blot analysis of transfected cell lysates. Moreover, indirect immunofluorescence analysis revealed an intense vpx staining pattern distributed evenly throughout the cytoplasm of transfected cells. This distribution differed markedly from cells expressing wild-type HIV-2 in which vpx localized to the inner surface of the plasma membrane. To determine whether other HIV components were required for this surface localization, we expressed vpx in the context of replication competent HIV-1 and HIV-2 proviruses. Following cotransfection with a vpx-deficient HIV-2 provirus (pXM7), eukaryotically expressed vpx targeted to the plasma membrane and colocalized with HIV-2 p27 gag in a pattern indistinguishable from wild-type HIV-2. Moreover, progeny virions from cotransfected Cos-1 cells contained wild-type amounts of vpx protein, demonstrating that vpx could be efficiently packaged in trans. Under the same experimental conditions, cotransfection of vpx with wild-type HIV-1 (pHXB2) and with vpr-deficient HIV-1 (pR2) failed to result in detectable cell surface targeting or virion incorporation of vpx despite its high level cellular expression. These results demonstrate that efficient intracellular transport and packaging of vpx require interaction with other type-specific virus components.

Amino Acid Sequence↗
PubMed1993

Analysis of hepatitis C virus capsid, E1, and E2/NS1 proteins expressed in insect cells.

The baculovirus/insect cell expression system was used to express the capsid protein and glycoproteins (e1 and e2/NS1) of the hepatitis C virus (HCV). Each polypeptide domain was expressed individually using two different constructs varying at their carboxy termini in order to retain or delete hydrophobic domains that may be involved in membrane association. The capsid proteins were transported to the nucleus where they formed a single large crystal-like inclusion. The capsid proteins were phosphorylated in insect cells. The e1 and e2 polypeptides were present in both the soluble and insoluble cellular fractions. Deletion of a hydrophobic domain in the carboxy terminus of e2 resulted in the polypeptide becoming soluble but not secreted. Deletion of the carboxy terminus of e1 had no effect on solubility. Both e1 and e2 were glycosylated, with variable glycosylation of e1 giving rise to a series of polypeptides varying in apparent molecular weight. Co-infection of insect cells with viruses expressing e1 and e2 resulted in a complex that permitted the coimmunoprecipitation of e1 with antibodies to e2 and vice versa. Immunofluorescence staining of insect cells expressing e1 and e2 indicated that reactivity to e2 was more prevalent in anti-HCV positive human sera.

Animals↗
PubMed1993

Extended-release formulation of morphine for subcutaneous administration.

Pain arising from cancer tends to be chronic and chemotherapy of cancer pain usually requires narcotics. Most injectable narcotics, however, have short half-lives (T1/2) and require either continuous infusion or repeated frequent injections which are both inconvenient and uncomfortable. An extended-release formulation of morphine sulfate (Depo/Morphine) in a lipid-based drug-delivery system was characterized and tested in an animal model. The encapsulation efficiency was 53% +/- 4%, and the in vitro release T1/2 in human plasma at 37 degrees C was 12.1 +/- 1.1 days. Following s.c. administration of Depo/Morphine, the total amount of morphine remaining at the s.c. injection site decreased monoexponentially with a T1/2 value of 2.59 +/- 0.16 days as compared with 0.46 +/- 0.04 h following the injection of unencapsulated morphine. The morphine concentration in plasma also decreased monoexponentially with a T1/2 value of 8.33 +/- 2.13 days as compared with 0.45 +/- 0.21 h for unencapsulated morphine. Cataleptic behavior was observed in mice injected with unencapsulated morphine but not in those given an identical dose of morphine in the form of Depo/Morphine. In conclusion, Depo/Morphine has potential as an extended-release formulation of morphine and may be useful in chemotherapy of cancer pain as well as in maintenance therapy of narcotic addicts.

Animals↗
PubMed1993

Nutritional status of Chinese-, Korean-, and Japanese-American elderly.

OBJECTIVE: To examine the nutritional status of three major subgroups of Asian-American elderly. SUBJECTS: The sample consisted of 169 Chinese, 90 Korean, and 50 Japanese elderly who lived in five apartment buildings for senior citizens in Chicago, Ill. MAIN OUTCOME MEASURES: Twenty-four-hour dietary recalls were used to evaluate dietary intake. Anthropometric measures of height, weight, and triceps skinfold thickness were also obtained. RESULTS: Many Asian-American elderly consume an inadequate amount of dietary calcium. A large percentage of Korean elderly also consume inadequate amounts of protein and vitamins A and C. Underweight was more common than obesity among these ethnic elderly groups. APPLICATIONS: The information in this article provides valuable data to the Asian-American community for program planning as well as to health providers who work with individual Asian-American elderly to meet their nutrition needs.

Aged↗
PubMed1993

Severe constipation with diffuse intestinal myenteric hyperganglionosis.

The authors report a case of neuronal intestinal dysplasia in a 6-year-old girl. The disease is characterized by hyperplastic ganglia throughout the large and small intestine, associated with severe constipation. To better understand the pathophysiology of this disease the authors investigated the histopathologic, ultrastructural, and immunohistochemical characteristics of the intestinal tissue in this case. The hyperganglionosis was associated with immunohistochemical findings of intact expression of the neuropeptides controlling the peristaltic reflex, through lower expression of calcitonin-gene related peptide. With the recent progress in our understanding of the neural regulation of gastrointestinal function, it may now be possible to begin to understand the complex pathophysiological mechanisms underlying gastrointestinal motility disorders.

Calcitonin Gene-Related Peptide↗
PubMed1993

Dependence of plaid motion coherence on component grating directions.

We measured motion coherence for plaids composed of two different spatial frequency (SF) cosine grating components moving at various relative angles. The component SFs were in a ratio of 6:1, and several component motion directions were chosen to produce small to large angular differences. For angles of less than +/- 45 deg all subjects perceived rigid coherent motion, while for angles of +/- 45 deg or greater the components were perceived to slide transparently. The results were not altered when we changed the ratio of component contrasts or speeds over a factor of 2 and varied the SF ratio up to 9:1. These results show that transparency or coherence of moving plaids in different spatial scales depends on the relative component motion directions and is relatively independent of contrast, speed, and SF difference between the components. This angular dependence also explains recent data previously thought to be based on a visual computation of multiplicative transparency. A quantitative model in which the resultant motion on each scale provides a facilitative biasing signal to units tuned to similar directions (within +/- 30 deg) on other scales explains the experimental results.

Contrast Sensitivity↗
PubMed1993

Dental follicular tissue: misinterpretation as odontogenic tumors.

The dental follicle is radiographically and histologically observed in association with unerupted or impacted teeth. However, this normal tissue structure is often confused with odontogenic tumors by pathologists with limited experience in evaluating jaw lesions. This study was designed to evaluate the incidence and possible reasons for incorrect interpretation of dental follicles. From 1970 to 1988, 847 dental follicles and/or dental papillas from 663 patients were submitted to the Armed Forces Institute of Pathology (AFIP) by medical pathologists seeking diagnostic consultation. Nearly 84% of patients were in the second and third decades of life. The male to female ratio was 1.4:1.0. Over 70% of specimens were obtained from around impacted third molar teeth. Fifty-three percent of specimens were correctly interpreted by the contributing pathologists. Only a descriptive interpretation was given for 17%, no diagnosis was made in 10%, and 20% were incorrectly diagnosed. In descending order, the most frequent incorrect diagnoses were odontogenic cyst, odontogenic myxoma, odontogenic fibroma, ameloblastic fibroma, odontoma, and ameloblastoma. Dental papillas were most frequently misdiagnosed as odontogenic myxomas. The histologic features and diagnostic pitfalls are discussed, as well as the need to consider the clinical, radiographic, and microscopic features in arriving at a final diagnosis.

Adolescent↗
PubMed1993

Pantherinine, a cytotoxic aromatic alkaloid, and 7-deazainosine from the ascidian Aplidium pantherinum.

A new cytotoxic aromatic alkaloid, pantherinine [1], and a mixture of nucleosides including 7-deazainosine [3], have been isolated from the ascidian Aplidium pantherinum collected at Stenhouse Bay, South Australia. The structures were determined primarily from 1H- and 13C-nmr data, especially one-bond and multiple-bond proton-carbon correlations. Although 7-deazainosine [3] has been known as a synthetic compound for several decades, this appears to be the first report of its isolation as a natural product.

Acridines↗