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Biomedical subjects

T M Shinnick

Publications and source records attributed to T M Shinnick.

At least 73 records · Page 4Linked to original sources
PubMed1985

Specific regulation of transcription of the discoidin gene family in Dictyostelium discoideum.

Dictyostelium discoideum strains that carry the dis mutations fail to express the family of developmentally regulated discoidin lectin genes during morphogenesis. We show here that this absence of discoidin lectin expression is due to the failure to transcribe the discoidin genes. Furthermore, the dis mutations appear to affect only discoidin expression and not the expression of other proteins during development, as assessed by a two-dimensional gel analysis of pulse-labeled proteins and by the accumulation of developmentally regulated enzymes. The dis mutations appear to define trans-acting regulatory loci, the products of which act at the transcriptional level to control specifically the developmental expression of the discoidin gene family.

DNA, Fungal↗
PubMed1984

Peptide-elicited protein-reactive antibodies in molecular biology and medicine.

A relatively short peptide can be used as an immunogen to elicit antibodies that are capable of reacting with full-length proteins containing the peptide's amino acid sequence. Such peptides are frequently represented in the primary sequence of a protein. The antibodies elicited by these peptides are directed against a specific region of the protein chosen in advance by the investigator and so have a predetermined specificity. In basic research, such antibodies are useful in identifying the gene product of an open reading frame, purifying enzymatically active proteins by immunoaffinity techniques, and investigating protein folding domains and immunogenic structure and function. In medicine, since some peptides are capable of eliciting antisera that can bind to and neutralize virus, the antibodies may be reagents for passive vaccination, antitoxin therapy, and targeted immunotherapy of neoplasia. The peptides themselves may serve as the basis for safe, chemically defined vaccines.

Amino Acid Sequence↗
PubMed1983

Glyceraldehyde 3-phosphate dehydrogenase protein and mRNA are both differentially expressed in adult chickens but not chick embryos.

We have determined the 679 nucleotide sequence of a cDNA clone which, by hybridization-translation experiments, corresponds to a 36K chick brain protein. Our studies provide a partial amino acid sequence for this protein, identifying it as chicken glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Antisera raised against purified chicken GAPDH reacted with a 36K protein present in chick brain extracts and estimated to be the fourth most prevalent protein, as determined by either Coomassie Blue staining or by in vitro translation of chick brain mRNA. The amounts of GAPDH mRNA in chick brain, liver and muscle and adult chicken brain are similar, whereas the relative amount of adult chicken muscle GPDH mRNA is greatly elevated and that of adult liver lowered. The GAPDH protein levels showed a similar variation between tissues, suggesting that the levels of GAPDH protein are largely regulated by the amount of available GAPDH mRNA. The chicken GAPDH clone does not hybridize to rat mRNA, even though GAPDH is one of the most evolutionarily conserved proteins, indicating that selection pressures are heavier at the primary protein sequence level than at the nucleic acid sequence level for this gene, a situation contrasting to that of the tubulins.

Amino Acid Sequence↗
PubMed1983

Antibodies that react with predetermined sites on proteins.

Contrary to previous predictions, relatively short synthetic peptides that mimic part of a protein sequence are routinely capable of eliciting an antiserum that reacts with the partially mimicked protein. Peptides capable of eliciting protein-reactive serums are frequently represented in the primary sequence of a protein, can be characterized by a set of simple chemical rules, and are confined neither to immunodominant regions of intact proteins nor to the amino or carboxyl terminals. As such, synthetic peptide immunogens are valuable for eliciting reagents with predetermined specificity that can be used for basic research. In addition, some synthetic peptides are capable of mimicking regions of virus proteins and eliciting immune responses in animals that are protective against the viral agents. Such peptides may thus serve as the basis for safe, chemically defined synthetic vaccines.

Antibody Specificity↗
PubMed1983

Identifying the protein products of brain-specific genes with antibodies to chemically synthesized peptides.

From the nucleotide sequences of three cDNA clones of rat brain-specific mRNAs, we deduced the partial amino acid sequences of two previously unknown proteins. We raised antisera to synthetic peptides mimicking short regions of these putative brain-specific proteins, and used these sera in immunocytochemical studies to localize each protein in the brain. One protein is found in large neurons throughout the brain, asymmetrically distributed toward the dendritic pole of the cell cytoplasm, suggesting involvement in the synthesis and/or directional transport of dendritic substances. The sequence of the second protein contains pairs of basic residues similar to precursors for neurotransmitters. The protein is located in (and may be the precursor for the neurotransmitter of) a novel fiber network of major extent with ramifications in cerebellum, hippocampus, and cortex, and in cell bodies in the brain stem, hypothalamus, and caudate nucleus. Our approach provides a direct method for characterizing rare brain molecules which may not have been anticipated and for which there are no known functional assays.

Amino Acid Sequence↗
PubMed1983

Mutants of Dictyostelium discoideum blocked in expression of all members of the developmentally regulated discoidin multigene family.

Mutant strains of D. discoideum are described that can complete morphogenesis and cytodifferentiation but which express vastly reduced levels of the galactose-binding lectins discoidin I and II (less than 1% and 1%-2% respectively) compared to the wild-type control. Mutant cells proceeding through development lack lectin activity, lectin protein, and specific lectin mRNA. In contrast, the genes encoding these proteins are present in their wild-type configurations in the genome. Since these proteins are encoded by four to five discrete genes, the mutations in these strains are most likely in genes involved in the regulation of the expression of members of this multigene family. The results also indicate that the discoidin lectins may not be required for fruiting body construction in this organism. Finally, coupled with the recent ability to transform D. discoideum, these mutants open the way to identification and isolation of regulatory genes and their products.

Cell Differentiation↗
PubMed1983

Chemically synthesized peptides of hepatitis B surface antigen duplicate the d/y specificities and induce subtype-specific antibodies in chimpanzees.

Synthetic peptides, predicted from the nucleotide sequence of the S gene of hepatitis B virus were analyzed in terms of the established specificities of the hepatitis B surface antigen. The analysis indicated that the group-specific alpha antigen is composed of at least three nonoverlapping sequences and that a relatively hydrophilic region of the surface antigen protein, spanning amino acid residues 110-137, specifies the major d and y subtype system. The d/y subtype appears to depend on changes in one or more variable amino acids at positions 127, 131, and 134 of the hepatitis B surface antigen protein. Peptide 49 (consisting of amino acid sequences of the y subtype for the region 110-137), coupled to a carrier protein and mixed with an adjuvant, stimulated a brisk anti-y response in chimpanzees, the relevant model of human response to hepatitis B virus immunization and infection. Experimental challenge with homologous hepatitis B virus resulted in a pattern of partial protection. The results offer promise for the application of chemically synthesized peptides as vaccines in the prophylaxis of hepatitis B virus disease.

Amino Acid Sequence↗
PubMed1983

Synthetic peptide immunogens as vaccines.

Synthetic peptide immunogens have been shown to elicit antibodies that can react with full-length proteins containing that peptide. Such antibodies are directed against a specific region of the protein chosen in advance by the investigator and so have a predetermined specificity. In basic research, these antibodies are useful in identifying the protein product of an open reading frame, localizing the gene product to particular cells or subcellular organelles, identifying the enzymatic function of a protein product, following the fate of particular regions of a product through protein maturation processes, analyzing the expression of exons following DNA rearrangements and RNA splicing, and purifying the protein by immunoaffinity chromatography techniques. In medicine, such antibodies may provide reagents for passive vaccination, antitoxin therapy, and targeted immunotherapy of neoplasia. The peptides themselves may be used as synthetic vaccines. The immediate future of the synthetic peptide immunogen in medicine is clear--the promise demonstrated in the laboratory must be reduced to safe application in the hospital. Two barriers to this are the selection of precisely the best peptide and the selection of the proper adjuvant. Currently, a brute force approach is utilized to find the best peptide for eliciting the desired antibodies. This is clearly a problem when the pathogenic organism is assayable only in man. Possibly, by combining studies on the antigenicity of the pathogenic organism with an analysis of naturally occurring variants that alter its immunogenicity, peptide selection will be made easier. Also, since the adjuvants and carriers used in the laboratory are in general too harsh for widespread use in humans and animals, much work needs to be done to find suitable adjuvants and carriers. Nonetheless, now that the major conceptual hurdle to synthetic peptide vaccines has been cleared (that is, it is not necessary to reproduce conformation exactly), it should be relatively straightforward to solve the remaining problems.

Animals↗
PubMed1982

Immunogenic structure of the influenza virus hemagglutinin.

We chemically synthesized 20 peptides corresponding to 75% of the HA1 molecule of the influenza virus. Antibodies to the majority (18) of these peptides were capable of reacting with the hemagglutinin molecule. These 18 peptides are not confined to the known antigenic determinants of the hemagglutinin molecule, but rather are scattered throughout its three-dimensional structure. In contrast, antibody raised to intact hemagglutinin did not react with any of the 20 peptides. Taken together these results suggest that the immunogenicity of an intact protein molecule is not the sum of the immunogenicity of its pieces.

Amino Acid Sequence↗
PubMed1981

Sequence-specific antibodies show that maturation of Moloney leukemia virus envelope polyprotein involves removal of a COOH-terminal peptide.

We followed maturation of the glycosylated envelope polyprotein Pr80env of a murine retrovirus by using antisera specific to subregions of the protein, including an antiserum directed against a synthetic peptide corresponding to the COOH-terminus of Pr80env. Shortly after synthesis and glycosylation, Pr80env is cleaved into two species, gp70 and Pr15E, that are found associated, perhaps through disulfide bonds, in infected cells. Pr15E is further cleaved at the time of virus maturation to form virus protein p15E. NH2-Terminal protein sequence analysis showed that Pr15E had an NH2 terminus in common with p15E. Pr15E, but not p15E, is precipitated by antibody against the COOH-terminal peptide; hence, p15E is missing a peptide at the COOH-terminus. Our data indicate that Pr15E is the predominant species in cells and p15E is the major species in virus.

Amino Acid Sequence↗
PubMed1981

Chemically synthesized peptides predicted from the nucleotide sequence of the hepatitis B virus genome elicit antibodies reactive with the native envelope protein of Dane particles.

Thirteen peptides corresponding to amino acid sequences predicted from the nucleotide sequence of the hepatitis B surface antigen were synthesized chemically. The free or carrier-linked synthetic peptides were injected into rabbits, and 7 of the 13 elicited an antipeptide response. Antisera against four of the six soluble peptides longer than 10 amino acids were reactive with native antigen and specifically precipitated the 23,000- and 28,000-dalton forms from Dane particles. As the hepatitis molecule had not been chosen for study because of any structural feature suggesting unique opportunities for success, these results suggest that the strategy is general and should work for any protein as long as enough domains are studied. Peptides such as these could prove to be ideal vaccines.

Amino Acid Sequence↗
PubMed1980

Chemical synthesis of a polypeptide predicted from nucleotide sequence allows detection of a new retroviral gene product.

We previously determined the nucleotide sequence of the 3' end of Moloney leukaemia virus and discovered the potential coding region for an unknown protein, R. We now show that this region does encode a protein. A pentadecapeptide of R was chemically synthesized and antibodies raised against it. Antisera to the synthetic peptide recognize the R protein and the env precursor polyprotein in infected cells. The strategy presented here should provide a general method for accessing proteins predicted by nucleotide sequences.

Amino Acid Sequence↗
PubMed1980

Nucleotide sequence of Moloney leukemia virus: 3' end reveals details of replications, analogy to bacterial transposons, and an unexpected gene.

We have determined the sequence of a cloned DNA fragment 1108 base pairs long which corresponds to the 3' end of the Moloney murine leukemia provirus. The clone was obtained as the primary product of reverse transcription and begins with the Moloney "strong stop" sequence, then extends towards the 5' end of the provirus. Our sequence: (i) proves that reverse transcriptase switches templates during minus strand synthesis; (ii) defines the limits of the 515-base-pair repeats which occupy both ends of the integrated provirus; (iii) shows that the structure of the proviral repeats has strong analogy to bacterial insertion sequences, indicating that the Moloney provirus is a transposon; (iv) identifies the putative promotor for genomic transcription within these repeats; (v) shows that the presumed origin of second strand synthesis, which lies just outside the 3' repeat, has tertiary structure analogous to single-stranded bacteriophage origins of replication; (vi) solves the amino acid sequence of most of pI5E, the carboxy-terminal product of the env gene; (vii) allows detailed mapping of the mink cell focus-forming virus substitution locus in a central location within the gp70 region of the env gene; and (viii) identifies a long open translation frame to the right of the env gene (R gene) which could be involved in leukemogenesis.

Animals↗
PubMed1980

The cbpA gene: role of the 26,000-dalton carbohydrate-binding protein in intercellular cohesion of developing Dictyostelium discoideum cells.

The loss of the lectin-like activity of a 26,000-dalton carbohydrate-binding protein (CBP-26) results in the loss of aggregation competence and cell-cell cohesiveness in developing cells of Dictyostelium discoideum. The lesion responsible for this phenotype behaves like a mutation in the structural gene for CBP-26, maps in linkage group II, and has been designated cbpA1. In aggregation-competent revertants, the degree of aggregation competence and cell-cell cohesiveness is directly related to the specific activity of CBP-26. Thus, CBP-26 appears to play an essential role in cell aggregation through the cell-cell cohesion process.

Cell Adhesion↗