Biomedical subjects

D B Teplow

Publications and source records attributed to D B Teplow.

At least 73 records · Page 4Linked to original sources

PubMed1990

Identification of cellular proteins binding to the scrapie prion protein.

The scrapie prion protein (PrPSc) is an abnormal isoform of the cellular protein PrPc. PrPSc is found only in animals with scrapie or other prion diseases. The invariable association of PrPSc with infectivity suggests that PrPSc is a component of the infectious particle. In this study, we report the identification of two proteins from hamster brain of 45 and 110 kDa (denoted PrP ligands Pli 45 and Pli 110) which were able to bind to PrP 27-30, the protease-resistant core of PrPSc on ligand blots. Pli 45 and Pli 110 also bound PrPC. Both Pli's had isoelectric points of approximately 5. The dissociation rate constant of the Pli 45/PrP 27-30 complex was 3 x 10(-6) s-1. Amino acid and protein sequence analyses were performed on purified Pli 45. Both the composition and the sequence were almost identical with those predicted for mouse glial fibrillary acidic protein (GFAP). Furthermore, antibodies to Pli 45 reacted with recombinant GFAP. The identification of proteins which interact with the PrP isoforms in normal and diseased brain may provide new insights into the function of PrPC and into the molecular mechanisms underlying prion diseases.

Amino Acid Sequence↗

PubMed1989

Interaction of distinct domains in Mu transposase with Mu DNA ends and an internal transpositional enhancer.

Bacteriophage Mu is the largest and most efficient transposable element known. The Mu transposase (A protein) of relative molecular mass 75,000 is a central component of the transposition machinery. We report here that the N-terminal region of Mu transposase contains two distinct DNA-binding domains, one which binds the two Mu DNA ends, and another which binds an internal operator region. This internal operator is required for the transposase-mediated synapsis and nicking of Mu ends in vitro, and stimulates transposition more than 100-fold in vivo. The orientation of the operator with respect to the ends is critical to its function, whereas its distance from the ends seems to be relatively unimportant. We propose that the operator enhances transposition by transiently interacting with the transposase and Mu DNA end(s) to form a complex in which synapsis of the ends occurs.

Bacteriophages↗

PubMed1988

Purification and properties of the cellular and scrapie hamster prion proteins.

During scrapie infection an abnormal isoform of the prion protein (PrP), designated PrPSc, accumulates and is found to copurify with infectivity; to date, no nucleic acid has been found which is scrapie-specific. Both uninfected and scrapie-infected cells synthesize a PrP isoform, denoted PrPC, which exhibits physical properties that differentiate it from PrPSc. PrPC was purified by immunoaffinity chromatography using a PrP-specific monoclonal antibody cross-linked to protein-A--Avidgel. PrPSc was purified by detergent extraction, poly(ethylene glycol) precipitation and repeated differential centrifugation of PrPSc polymers. Both PrP isoforms were found to have the same N-terminal amino acid sequence which begins at a predicted signal peptide cleavage site. The first 8 residues of PrPC were found to be KKXPKPGG and the first 29 residues of PrPSc were found to be KKXPKPGGWNTGGSXYPGQGSPGGNRYPP. Arg residues 3 and 15 in PrPSc and 3 in PrPC appear to be modified since no detectable signals (denoted X) were found at these positions during gas-phase sequencing. Both PrP isoforms were found to contain an intramolecular disulfide bond, linking Cys 179 and 214, which creates a loop of 36 amino acids containing the two N-linked glycosylation sites. Development of a purification protocol for PrPC should facilitate comparisons of the two PrP isoforms and lead to an understanding of how PrPSc is synthesized either from PrPC or a precursor.

Amino Acid Sequence↗

PubMed1988

Structure-function relationships in the transposition protein B of bacteriophage Mu.

The B-protein of phage Mu, which is required for high frequency intermolecular transposition in vivo, shows ATPase activity in vitro, binds nonspecifically to DNA, and stimulates intermolecular strand transfer. To elucidate the structural bases for B-protein function, it was subjected to limited proteolysis with two different proteases, trypsin and chymotrypsin. The resulting fragments were mapped by amino acid sequencing. These data show that the B-protein is organized in two domains: an amino-terminal domain of 25 kDa and a carboxyl-terminal domain of 8-kDa. A fragment analogous to the amino-terminal domain, produced by deleting the 3' end of a cloned B gene, proved to be insoluble and had to be renatured after elution from a sodium dodecyl sulfate gel. The renatured protein retains ATP-binding activity and to a lesser extent the DNA-binding activity of the MuB protein, but is unable to hydrolyze ATP or function in transposition. We also show in this study that efficient DNA-strand transfer by the B-protein occurs even in the absence of a detectable ATPase activity or in the presence of adenosine 5'-O-(thio)triphosphate (ATP gamma S).

Adenosine Triphosphate↗

PubMed1987

Identification of cDNA clones of the mouse neural cell adhesion molecule L1.

Two cDNA clones of the neural cell adhesion molecule L1 (Mr 200,000) were isolated using lambda gt10 and lambda gt11 libraries constructed from postnatal day 8 mouse brain poly(A)+ RNA. Clone K21 was selected and identified using immunoaffinity purified polyclonal antibodies. It was then used to isolate a secondary clone (K21-1), which hybridized with an oligonucleotide probe synthesized by reverse translation of the aminoterminal sequence of the 80 kDa carboxyterminal proteolytic fragment of L1. Blot hybridization analysis indicated that L1 is encoded by a single gene and transcribed by a single 6 kb mRNA which is present only in cells or tissues known to express L1.

Animals↗

PubMed1987

Structural domains in phage Mu transposase: identification of the site-specific DNA-binding domain.

Limited proteolysis of phage Mu transposase with three proteases of differing specificities produced a common pattern of fragmentation. The fragments were mapped by using a combination of immunoblotting and amino acid sequence analysis. Our results suggest that the transposase molecule is organized principally into three domains: an amino-terminal domain of molecular mass 30 kDa, a core region of approximately 35 kDa, and a carboxyl-terminal domain of approximately 10 kDa. The amino-terminal domain has at least two additional sites that are partially accessible to proteases. Filter binding and nuclease protection studies were done to determine the functions of the isolated domains. Site-specific binding to Mu DNA was localized to the amino-terminal domain. The core domain showed nonspecific DNA-binding activity.

Amino Acid Sequence↗

PubMed1986

Microscale structure analysis of a high-molecular-weight, hydrophobic membrane glycoprotein fraction with platelet-derived growth factor-dependent kinase activity.

General methods for the study of the primary structure of picomole quantities of large, hydrophobic membrane glycoproteins with blocked amino-termini have been developed. Three techniques designed to be used in concert with each other are described: first, modified protein preparation and fragmentation techniques; secondly, a simple but very selective two-dimensional reversed-phase high-performance liquid chromatography system for the resolution of complex mixtures of small to medium-sized tryptic peptides on Vydac C4, C18 and diphenyl columns and thirdly, a two-dimensional separation method for large, denaturated (CNBr) polypeptide fragments by size-exclusion high-performance liquid chromatography, combined with either reversed-phase high-performance liquid chromatography (C4) or sodium dodecyl sulphate polyacrylamide gel electrophoresis in conjunction with electroblotting and autoradiography. These methods were applied to studies of the platelet-derived growth factor receptor. Starting with 500 pmoles of purified protein, a total of 232 amino acids were sequenced.

Alkylation↗

PubMed1986

Electroblotting onto activated glass. High efficiency preparation of proteins from analytical sodium dodecyl sulfate-polyacrylamide gels for direct sequence analysis.

We have developed a new method for the isolation of proteins for microsequencing. It consists of electrophoretic transfer (electroblotting) of proteins or their cleavage fragments onto activated glass filter paper sheets immediately after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteins are immobilized on the glass fiber sheets by ionic interactions or by covalent attachment. A wide range of proteins can be prepared in this fashion with no apparent restriction due to solubility, size, charge, or other intrinsic properties of the proteins. As little as 50 ng of the transferred proteins can be detected using Coomassie Blue or fluorescent dye staining procedures and even smaller amounts of radiolabeled proteins by autoradiography. After detection, the protein-containing bands or spots are cut out and inserted directly into a gas-phase sequenator. The piece of glass fiber sheet acts as a support for the protein during the sequencing. Amounts of protein in the 5- to 150-pmol range can be sequenced, and extended runs can be obtained from the blotted samples because of improved stepwise yields and lower backgrounds. The method has been successfully applied to the sequencing of a variety of proteins and peptides isolated from one-dimensional and two-dimensional polyacrylamide gels.

Amino Acid Sequence↗

PubMed1986

Partial N-terminal amino acid sequences of three nonstructural proteins of two flaviviruses.

Partial N-terminal amino acid sequences for the three largest nonstructural proteins of two flaviviruses, yellow fever virus and St. Louis encephalitis virus, have been obtained. The determined sequences of these proteins exhibit significant amino acid sequence homology, and allow the positioning of these three nonstructural proteins in the polyprotein sequence deduced from the nucleotide sequence of yellow fever virus (C. M. Rice, E. M. Lenches, S. R. Eddy, S. J. Shin, R. L. Sheets, and J. H. Strauss, 1985, Science 229, 726-733.) The deduced start points support the hypothesis that the N terminus of nonstructural glycoprotein NS1 results from cleavage by signalase, whereas the N termini of NS3 and NS5 result from cleavages following double basic residues that are flanked by amino acids with short side chains.

Amino Acid Sequence↗

PubMed1986

A partial genomic DNA clone for the alpha subunit of the mouse complement receptor type 3 and cellular adhesion molecule Mac-1.

A genomic clone coding for the alpha subunit of the mouse complement receptor type 3 and the cellular adhesion molecule Mac-1 has been isolated directly from a genomic library using synthetic oligonucleotide probes based on the amino-terminal amino acid sequence of the protein. The identity of the clone has been established by DNA sequencing and in vitro translation of hybrid-selected mRNA. The gene is present in a single copy in the murine genome. The region containing the amino-terminal exon has been sequenced. RNA gel blotting shows that the Mac-1 alpha-subunit mRNA is 6 kilobases in length. Mac-1 alpha-subunit mRNA is present in macrophages but not T lymphoma or L cells. During gamma interferon-stimulated maturation of the mouse premyelocytic cell line M1, Mac-1 alpha-subunit mRNA is induced. This corresponds with the tissue distribution of the Mac-1 alpha subunit, showing expression is regulated at least partially at the message level.

Animals↗

PubMed1986

Primary structure of the human melanoma-associated antigen p97 (melanotransferrin) deduced from the mRNA sequence.

p97 is a cell-surface glycoprotein that is present in most human melanomas but only in trace amounts in normal adult tissues. To determine the structure of this tumor-associated antigen and to identify its functional domains, we have purified and cloned p97 mRNA and determined its nucleotide sequence. The mRNA encodes a 738-residue precursor, which contains the previously determined N-terminal amino acid sequence of p97. After removal of a 19-residue signal peptide, the mature p97 molecule comprises extracellular domains of 342 and 352 residues and a C-terminal 25-residue stretch of predominantly uncharged and hydrophobic amino acids, which we believe acts as a membrane anchor. Each extracellular domain contains 14 cysteine residues, which form seven intradomain disulfide bridges, and one or two potential N-glycosylation sites. Protease digestion studies show that the three major antigenic determinants of p97 are present on the N-terminal domain. The domains are strikingly homologous to each other (46% amino acid sequence homology) and to the corresponding domains of human serum transferrin (39% homology). Conservation of disulfide bridges and of amino acids thought to compose the iron binding pockets suggests that p97 is also related to transferrin in tertiary structure and function. We propose that p97 be renamed melanotransferrin to denote its original identification in melanoma cells and its evolutionary relationship to serotransferrin and lactotransferrin, the other members of the transferrin superfamily.

Amino Acid Sequence↗

PubMed1986

Unusual phylogenetic conservation of the N-terminal amino acid sequence of the central nervous system-specific membrane glycoprotein F3-87-8 (CNSgp130).

CNSgp130 is a CNS-specific membrane glycoprotein abundantly expressed throughout the mature mammalian CNS. The molecule is recognised by the mouse monoclonal antibody F3-87-8, which reacts with a determinant of CNSgp130 common to all mammals tested to date. Rat and human CNSgp130 were purified by a combination of F3-87-8 monoclonal antibody affinity and gel permeation chromatography, and the N-terminal amino acid sequence was determined by gas-phase sequencing techniques. The results show a remarkable conservation of the N terminus of the CNSgp130 polypeptide between rats and humans, with complete identity of the first 20 amino acid residues. There was an unusually high and phylogenetically conserved number of cysteines in this region. The sequence showed no homology to other known sequences and should prove useful in precisely identifying the relationship of CNSgp130 to other CNS membrane molecules.

Amino Acid Sequence↗

PubMed1985

Biosynthesis and membrane topography of the neural cell adhesion molecule L1.

The biosynthesis and membrane topography of the neural cell adhesion molecule L1 have been studied in cerebellar cell cultures by metabolic labeling and immunoprecipitation. Pulse and pulse-chase experiments with [35S]methionine show that L1 is synthesized in its high mol. wt. form, the 200 kd component. The lower mol. wt. components with 40, 80 and 140 K apparent mol. wts. can be generated by proteolysis in intact cellular membranes. Peptide maps generated by protease treatment of L1 isolated from adult mouse brain show that the 80 and 140 kd components are related to the 200 kd component, but not to each other. The 200, 80 and 40 kd components can be biosynthetically phosphorylated. The 140 kd component is not phosphorylated and not released from the surface membrane during tryspinization. The phosphorylated amino acid is serine. In the presence of tunicamycin the 200 kd component is synthesized as a 150 kd protein. Pulse-chase experiments in the presence of tunicamycin indicate that the carbohydrate moieties are predominantly N-glycosidically linked and that the contribution of O-glycosylation is minimal. The carbohydrate moieties are of the complex type as shown by treatment with endoglycosidase H. Since monensin inhibits processing of the carbohydrate moieties, the 200 kd component appears to be transported to the surface membrane via the Golgi apparatus.

Amino Acids↗

PubMed1985

Identification of a peptide fragment from the carboxyl-terminal extension region (E-domain) of rat proinsulin-like growth factor-II.

A fragment of the carboxyl-terminal extension region (E-peptide) of rat proinsulin-like growth factor-II has been purified from medium conditioned by cultured BRL-3A rat liver cells. The fragment, identified by microsequence analysis, was discovered in a biologically active fraction of insulin-like growth factor II (IGF-II). The fragment begins at position 117 in pro-IGF-II, two amino acids downstream from an Arg-Arg potential prohormone processing site. A synthetic analogue of the E-peptide at high concentrations stimulates [3H]thymidine incorporation in NIL8 hamster cells, raising the possibility that the E-peptide might bind with low affinity to a mitogen receptor. Peptides from the E-regions of pro-IGF-I and pro-IGF-II should be useful for development of radioimmunoassays for measurement of the somatic production of IGF-I and IGF-II, analogous to the radioimmunoassay for the insulin C-peptide.

Amino Acid Sequence↗

PubMed1985

A cellular gene encodes scrapie PrP 27-30 protein.

A clone encoding PrP 27-30, the major protein in purified preparations of scrapie agent, was selected from a scrapie-infected hamster brain cDNA library by oligonucleotide probes corresponding to the N terminus of the protein. Southern blotting with PrP cDNA revealed a single gene with the same restriction patterns in normal and scrapie-infected brain DNA. A single PrP-related gene was also detected in murine and human DNA. PrP-related mRNA was found at similar levels in normal and scrapie-infected hamster brain, as well as in many other normal tissues. Using antisera against PrP 27-30, a PrP-related protein was detected in crude extracts of infected brain and to a lesser extent in extracts of normal brain. Proteinase K digestion yielded PrP 27-30 in infected brain extract, but completely degraded the PrP-related protein in normal brain extract. No PrP-related nucleic acids were found in purified preparations of scrapie prions, indicating that PrP 27-30 is not encoded by a nucleic acid carried within the infectious particles.

Amino Acid Sequence↗

PubMed1985

Cloning and characterization of the myelin basic protein gene from mouse: one gene can encode both 14 kd and 18.5 kd MBPs by alternate use of exons.

A mouse cosmid library was screened with a cDNA clone for rat small (M, 14,000) myelin basic protein (MBP). The entire MBP gene was isolated. Five exons were detected with the cDNA clone, which encode the Mr 14,000 MBP. A sixth exon, detected using a synthetic oligonucleotide, encodes the 41 amino acids specific to the Mr 18,500 form of MBP. Splicing together all six exons would give rise to Mr 18,500 MBP, while an mRNA omitting exon V would be translated to produce Mr 14,000 MBP. Further experiments indicate that there is probably a single MBP gene in the mouse genome, and that there is a single major 5' end for mouse MBP transcripts, 47 bp 5' of the initiator methionine codon.

Animals↗

PubMed1985

High performance liquid chromatographic separation of the globin chains of non-human hemoglobins.

High performance liquid chromatography has been applied to the separation of the globin chains of 16 non-human species which include common mammalian and avian species. The procedure uses a large-pore C4 column which has been effectively employed for the separation of human globin chains. In many cases, the gradient for human chains with trifluoroacetic acid-water-acetonitrile was satisfactory or required only moderate modification. The separations were excellent for all except dog hemoglobin. Many results substantiate prior published information about heterogeneity, amino acid composition, etc. of the individual hemoglobins. Additional data on some of these hemoglobins have also been obtained, and some previously unstudied hemoglobins have been examined.

Animals↗

PubMed1984

Homologies between signal transducing G proteins and ras gene products.

The guanosine triphosphate-binding proteins (G proteins) found in a variety of tissues transduce signals generated by ligand binding to cell surface receptors into changes in intracellular metabolism. Amino acid sequences of peptides prepared by partial proteolysis of the alpha subunit of a bovine brain G protein and the alpha subunit of rod outer-segment transducin were determined. The two proteins show regions of sequence identity as well as regions of diversity. A portion of the amino-terminal peptide sequence of each protein is highly homologous with the corresponding region in the ras protein (a protooncogene product). These similarities suggest that G proteins and ras proteins may have analogous functions.

Amino Acid Sequence↗