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Biomedical subjects

J E Smart

Publications and source records attributed to J E Smart.

At least 19 recordsLinked to original sources
PubMed2005

Neutron detection via bubble chambers.

Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

Journal Article↗
PubMed1990

Purification of the IL-2 receptor (TAC) by ligand-affinity chromatography and utilization of the immobilized receptor for receptor-affinity chromatography (RAC) purification of IL-2, mutant IL-2, and IL-2 fusion proteins.

Recombinant technology has facilitated the production of two soluble forms of human p55 interleukin-2 receptor (IL-2R) in Chinese hamster ovary cells. We have developed a ligand-affinity method for the medium-scale purification of these two soluble forms of the IL-2R, based on the biochemical interactions between the matrix-bound ligand (interleukin-2) and its soluble receptor. The affinity-purified IL-2R is further purified by anion-exchange chromatography followed by gel filtration. This method has provided enough highly pure IL-2R for structure and function studies and for use in practical applications such as high-flux drug-screening assays. The purified IL-2R subsequently has been immobilized on silica gel and employed for the purification of recombinant IL-2. Receptor-affinity-chromatography-purified IL-2 contains only a highly active monomeric form of the lymphokine, in contrast to immunoaffinity chromatography where several molecular forms of IL-2 with varying degrees of biologic activity are recovered. Receptor-affinity chromatography has been successfully applied to the purification of several mutant IL-2 as well as an IL-2-Pseudomonas exotoxin (IL2-PE40) fusion protein that is a 54.5-kDa chimeric protein in which the cell recognition domain is replaced by IL-2. The IL-2-PE40 is a potential cytotoxic agent for cells bearing the IL-2 receptor.

ADP Ribose Transferases↗
PubMed1988

Structural and partial amino acid sequence analysis of the human hemopoietic progenitor cell antigen CD34.

Monoclonal antibodies of the CD34 class all recognize a monomeric cell surface antigen of approximately Mr 110,000 which is selectively expressed on human hemopoietic progenitor cells. This structure can be readily surface-labeled with [125I]actoperoxidase and by periodate-[3H]borohydride, but it labels only weakly with [35S]methionine, [35Sl]cysteine, 3H-amino acids, or 3H-mannose, even after prolonged labeling periods. However, the antigen is more efficiently labeled by [3H]glucosamine. Lectin binding studies, sensitivity to certain glycosidases, and gel filtration analysis of glycans released by alkaline hydrolysis indicate that this glycoprotein contains several complex-type N-linked glycans as well as several highly sialylated O-linked glycans. Western blotting experiments show that various CD34 antibodies fail to efficiently detect desialylated and/or de-N-glycosylated forms of the antigen. Experiments involving the use of tunicamycin, together with metabolic labeling studies, strongly suggest that this structure "turns over" very slowly in vivo. The CD34 antigen is not detectably labeled by 32P-phosphate in vivo, nor are immune complexes containing it associated with phosphokinase activity in vitro. Sequential immunoprecipitation and Western blotting studies indicate that this antigen is not a member of the leukosialin/sialophorin family despite the fact that these molecules share several structural similarities. Partial amino acid analysis of highly purified CD34 antigen revealed no significant sequence similarity with any previously described structures.

Amino Acid Sequence↗
PubMed1987

Clathrin light chains LCA and LCB are similar, polymorphic, and share repeated heptad motifs.

The clathrin light chains fall into two major classes, LCA and LCB. In an intact clathrin triskelion, one light chain, of either class, is bound to the proximal segment of a heavy chain leg. Analysis of rat brain and liver complementary DNA clones for LCA and LCB shows that the two light chain classes are closely related. There appear to be several members of each class having deletions of varying length aligned at the same position. A set of ten heptad elements, characteristic of alpha-helical coiled coils, is a striking feature of the central part of each derived amino acid sequence. These observations suggest a model in which the alpha-helical segment mediates binding to clathrin heavy chains and the amino- and carboxyl-terminal segments mediate interactions with other proteins. They also suggest an explanation for the observed tissue-dependent size variation for members of each class.

Amino Acid Sequence↗
PubMed1986

Structure of turnip crinkle virus. III. Identification of a unique coat protein dimer.

The minor structural protein (p80), found in about one copy per virion in turnip crinkle virus (TCV), is shown by amino acid analysis and peptide mapping to be a covalent dimer of the major coat protein (p40). The covalent linkage occurs near the N termini of the crosslinked chains. These data suggest that TGV and related viruses contain 178 copies of p40 (89 non-covalent dimers) and one copy of p80 (covalent dimer of two additional p40 chains). The presence of p80 in the salt-stable RNA-protein complex formed when TCV dissociates, as described in an accompanying paper, indicates that the covalent modification affects binding to RNA. We suggest that p80 might be the final dimer to be incorporated into the shell and that it might also be the site for initiation of uncoating.

Amino Acids↗
PubMed1986

Disulfide scrambling of interleukin-2: HPLC resolution of the three possible isomers.

Native interleukin-2 (IL-2) contains three cysteines; two exist in a disulfide bridge (Cys-58 and Cys-105) and the third Cys-125 is a free sulfhydryl. In the presence of 6 M guanidine hydrochloride at alkaline pH, IL-2 is converted into three isomers. Each isomer represents one of the three possible disulfide-linked forms that can be generated from three cysteines. These three isomers were resolved on a C4 reverse-phase HPLC system. The identity of each of the three forms was determined by carboxymethylation of the free cysteines in each isomer with [3H]iodoacetic acid followed by determination of the labelled cysteines by tryptic peptide mapping. Tryptic peptide mapping of the more predominant of the two scrambled peaks showed it to be the Cys-105-S-S-Cys-125 linked form of IL-2. A Ser-125 construction of IL-2, which lacks a free cysteine, did not scramble under these conditions. These experiments demonstrate the utility of reverse-phase HPLC in studies of protein folding and disulfide bond structure.

Amino Acid Sequence↗
PubMed1986

Purification and partial sequence analysis of a 37-kDa protein that inhibits phospholipase A2 activity from rat peritoneal exudates.

We have purified from rat peritoneal exudates a 37-kDa protein that inhibits phospholipase A2 activity. It is the predominant phospholipase inhibitor protein in these preparations and also is detected in a wide variety of cell lines. Levels of expression range from 0 to 0.5% of total protein. In the peritoneal preparations, the inhibitor is partially proteolyzed into a series of lower mass forms, including species at 30, 24, and 15 kDa. These fragments all are immunoreactive with an antibody raised against the 37-kDa protein. The rat protein also is immunoreactive with an antibody developed against a 6-kDa phospholipase inhibitor protein from snake venom. The primary structure of more than half of the rat inhibitor has been deduced by protein microsequence analysis. These sequences are closely related to sequences from its human analogue, which we recently cloned and expressed (Wallner, B. P., Mattaliano, R. J., Hession, C., Cate, R. L., Tizard, R., Sinclair, L. K., Foeller, C., Chow, E. P., Browning, J. L., Ramachandran, K. L., and Pepinsky, R. B. (1986) Nature, in press), and thus we infer that the inhibitor is highly conserved evolutionarily. Properties of the molecule suggest that it is a member of a family of steroid-induced anti-inflammatory proteins collectively referred to as lipocortin.

Amino Acid Sequence↗
PubMed1986

Isolation and purification of the human thymocyte antigens T6 and M241.

T6 and M241 antigens are products of the Class I major histocompatibility complex. The T6 and M241 antigens can be detected on human cortical thymocytes and on dendritic cells in the skin by monoclonal antibodies. Here we report a method of purification of the T6 and M241 antigens. Amino acid sequence data of purified antigens indicate that the heavy chains are blocked at their N-termini, whereas the partial N-terminal amino acid sequence of the light chains is identical to that of the human beta 2-microglobulin. In order to obtain sequence data from the heavy chains a method is described for isolation of purified cyanogen bromide fragments by electrophoretic methods.

Amino Acid Sequence↗
PubMed1986

Purification of human erythropoietin to homogeneity by a rapid five-step procedure.

Human urinary erythropoietin (Ep) has been purified using a simple five-step procedure to yield preparations with potencies of 80,000 U/mg in 25% yield. The five steps involve: (1) affinity chromatography on CM Affi-Gel Blue, (2) chromatofocusing, (3) wheat germ lectin (or hydroxylapatite) chromatography, (4) reverse-phase high-performance liquid chromatography (HPLC) using a phenyl column, and (5) preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Ep activity was determined at each stage using a highly sensitive and specific in vitro assay that measures [3H]-thymidine incorporation into erythroid cells from spleens of phenylhydrazine-treated mice. The step 5 material was also tested with the in vivo polycythemic mouse assay procedure and was found to have a similar potency to that obtained in the [3H]-thymidine in vitro assay. SDS-PAGE analysis of the step 5 material revealed a single 38.5-kd band that comigrated with Ep bioactivity. Homogeneity was confirmed by amino acid sequence analysis. Starting with urine containing approximately 13 U/mg of protein, the cumulative degrees of purification achieved with each step were: step 1,25-fold; step 2, 75-fold; step 3, 300-fold; step 4, 1,500-fold; and step 5, 5,000-fold. Corresponding overall recoveries after each step were: greater than 100%, 70%, 45%, 30%, and 25%. These recoveries could be obtained when as little as 5,000 U of starting urinary Ep were processed because of the introduction of Tween 20 and SDS into buffers used at various stages of the purification procedure. In addition, a rapid method for determining Ep purity which involves reverse-phase HPLC of trypsinized 125I-labeled Ep is presented. This allows the establishment of purity with far less material than is required for amino acid sequencing.

Amino Acid Sequence↗
PubMed1985

Filipino workers in the Middle East: social profile and policy implications.

The characteristics of international labor migrants from the Philippines are examined. "Based on an analysis of a sample of 495 Middle East workers and 1983 worker placements, this paper presents a profile of Filipino workers in the Middle East with reference to such variables as occupation, gender, age and work experience, civil status, education, Philippine residence, household size and number of dependents." (summary in FRE, SPA)

Africa↗
PubMed1984

Genes encoding the Ti beta subunit of the antigen/MHC receptor undergo rearrangement during intrathymic ontogeny prior to surface T3-Ti expression.

To obtain further information about the ontogeny of the T-cell antigen/MHC receptor, a Ti beta subunit cDNA probe and heteroantisera specific for the Ti alpha and Ti beta subunits were utilized to characterize human T-lineage cells. Analysis of thymic tumors and normal thymocytes at both the DNA and protein levels demonstrates that Ti beta gene rearrangement is evident in stage II (T11+T6+T3-) and stage III (T11+T6-T3+), but not stage I (T11+T6-T3-) thymocytes. In contrast, surface expression of Ti alpha and Ti beta molecules is exclusively restricted to stage III thymocytes. Thus human T-lineage ontogeny is characterized by an orderly series of differentiation steps wherein Ti beta gene rearrangement precedes surface expression of the T3-Ti molecular complex.

Cloning, Molecular↗
PubMed1984

Early region 1B of adenovirus 2 encodes two coterminal proteins of 495 and 155 amino acid residues.

Partial sequence analysis of tryptic peptides has identified the E1B-495R (E1b-57K) (early transcription region 1B of 495 amino acid residues, with an approximate molecular weight of 57,000) protein of adenovirus 2 as encoded by the 495 amino acid open reading frame located in the adenovirus 2 DNA sequence between nucleotides 2016 and 3500. Additional proteins of 16,000 Mr and 18,000 Mr that are related to the E1B-495R protein were identified by cell-free translation of hybridization-selected mRNA. Analysis of [35S]methionine-containing amino terminal tryptic peptides by thin-layer chromatography showed that the E1B-495R, E1B-18K, and E1B-16K proteins all begin at the same initiation codon. The E1B-495R protein from 293 cells also has the same initial tryptic peptide, acetyl-methionyl-glutamyl-arginine. Sequence analysis of E1B-18K tryptic peptides indicated that this protein also has the same carboxy terminus as the E1B-495R protein and that it is derived from an mRNA that is spliced to remove sequences between nucleotides 2250 and 3269, resulting in a protein product of 155 amino acid residues. Analysis of E1B-16K tryptic peptides has not yet revealed the carboxy terminal structure of this protein. Both the E1B-495R and the E1B-155R (E1B-18K) proteins, as well as the E1B-16K protein, were precipitated from cell-free translations and from extracts of infected cells by antiserum against an amino terminal nonapeptide common to these proteins.

Adenovirus Early Proteins↗
PubMed1983

Structural characterization of the proteins encoded by adenovirus early region 2A.

Proteins encoded by adenovirus type 2 and type 5 early region 2A isolated from infected HeLa cells were compared to translation products of E2A-specific messenger RNA in a reticulocyte cell-free system and in Xenopus oocytes. The main cell-free translation product is a 72,000 Mr polypeptide which in HeLa cells as well as in Xenopus oocytes is converted into a 75,000 Mr phosphoprotein capable of binding to single-stranded DNA. Some minor proteins are proteolytic cleavage products of the major protein. In the cell-free system, three E2A polypeptides, 32,000, 37,000 and 44,000 Mr, are translated from minor polyadenylated mRNA species that can be separated from the major mRNA. Synthesis of all E2A polypeptides in vitro is inhibited by cap-analogs. The 44,000 Mr protein is also synthesized in Xenopus oocytes. Tryptic peptide maps of [35S]methionine-labeled E2A proteins were constructed using high pressure liquid chromatography and the position of the methionyl residues within each peptide was determined by amino acid sequencing procedures. This information and the DNA sequence of the adenovirus 5 E2A gene published by Kruijer et al. (1981) were used to align the peptides and to construct a map of the E2A proteins. Our data demonstrate that the major 75,000 Mr protein is coded for by a leftward reading frame of 529 amino acid residues located between 62 and 66 map units. The data also map six sites as targets for proteolytic enzymes. The minor E2A translation products have the same carboxy terminus as the major protein. The initiation codons of the 44,000, 37,000 and 32,000 Mr polypeptides probably correspond to amino acids 170, 243 or 244 and 290 of the major protein. Some functional properties of the major E2A protein are shared by the minor proteins and thus could be mapped. Major sites of phosphorylation, the region involved in binding to single-stranded DNA and the antigenic regions recognized by immune sera are located between amino acid residues 50 to 120, 170 to 470 and 170 to 240, respectively.

Adenoviruses, Human↗
PubMed1983

Analysis of expression of adenovirus DNA (fragments) by microinjection in Xenopus oocytes. Independent synthesis of minor early region 2 proteins.

Injection of whole adenovirus DNA into Xenopus oocytes results in the synthesis of large amounts of the early region 2A DNA-binding protein (E2A-DBP) and smaller amounts of polypeptide IX. The lack of synthesis of any functional messenger RNAs transcribed from the major late promotor at 16.3 map units is remarkable. Cleavage of the adenovirus DNA outside the E2A gene proper by restriction enzymes decreases synthesis of the DBP to about 10% of the amount produced after injection of intact DNA. On the other hand, presence of the terminal (Bellett) protein on the injected template enhances DBP synthesis considerably. Experiments with injected DNA restriction fragments, as well as reconstructed genes cloned into pBR322, indicate that efficient synthesis of DBP in oocytes requires the presence of either or both of the two main promoters from which the E2A gene is transcribed plus an intact 3' end of the gene. In the absence of any known promotor, 100-fold lower amounts of otherwise normal DBP are produced. Unlike in a regular infection, synthesis of DBP in oocytes does not require the product of the E1A gene. The same series of experiments also demonstrates that the DBP, a phosphoprotein, is the substrate of a cellular rather than a virus-encoded protein kinase. Two minor E2A proteins, although colinear with the major DBP, are synthesized independently. Synthesis of a 44,000 Mr protein, probably corresponding to the carboxy-terminal 360 amino acid residues of the DBP, is not decreased after injection of "promotorless" E2A genes. Unlike the 44,000 Mr protein, production of a 67,000 Mr protein (carboxy-terminal 483 amino acid residues) by one DNA-construct is probably directed by a T-A-T-A-A-A-T-A sequence in the vector DNA.

Adenoviruses, Human↗
PubMed1982

Co-existence of vinculin and a vinculin-like protein of higher molecular weight in smooth muscle.

Recently, a protein component of adhesion plaques with a molecular weight of 130,000 (named vinculin) has been purified from smooth muscle and non-muscle cells. As detected by immunological methods, the only vinculin-related polypeptides in fibroblasts are proteins of Mr = 130,000. However, we show here that smooth muscle contains, in addition to vinculin, an apparently distinct protein with a Mr = 152,000 that shares both structural and immunological features with vinculin. Amino acid analysis, peptide mapping, and antibody cross-reaction studies were used to elucidate these similarities. Mr = 152,000 protein seems to be restricted to muscle (mainly or exclusively to smooth muscle). The possibility that vinculin is derived from proteolytic processing of the Mr = 152,000 protein or that the proteins are related by some other type of post-translational modification appears unlikely (although this cannot be completely ruled out) since both proteins are made in a rabbit reticulocyte cell-free translation system when mRNA derived from smooth muscle is used as the template. Both proteins are capable of used as the template. Both proteins are capable of lowering the viscosity of F-actin solutions, although the activity of the Mr = 152,000 protein is stimulated by Ca2+ while the activity of smooth muscle vinculin is not.

Amino Acids↗