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Biomedical subjects

G L Ada

Publications and source records attributed to G L Ada.

At least 91 records · Page 5Linked to original sources
PubMed1976

Cytotoxic T cells recognize very early, minor changes in ectromelia virus-infected target cells.

Target cells (P-815 mastocytoma cells) infected with ectromelia virus became susceptible to lysis by H-2 compatible specific effector T cells within one hour of exposure of the cells to virus. This is long before viral progeny are produced and shed from the cell. Polyacrylamide gel electrophoresis (PAGE) profiles of the plasma membranes from infected and uninfected P-815 cells pulsed with 35S-methionine for one or a few hours after infection with virus were very complex and showed no consistent differences. P-815 cells, infected with ectromelia virus in the presence of an inhibitor of protein synthesis, pactamycin, slowly became susceptible to cell mediate lysis when the pactamycin was removed. The number of polypeptide species synthesized under these conditions was reduced to only three, of molecular weights between 10,000-50,000 daltons. Specific, newly synthesized membrane components recognized by mouse convalescent sera were isolated by immune complexing and examined by PAGE. Six polypeptide bands were seen, the major one correlating with one observed in the pactamycin experiment. The results suggested that the convalescent serum recognized both viral and host cell coded antigens. The significance of these findings is discussed.

Animals↗
PubMed1976

Changes in the surface of virus-infected cells recognized by cytotoxic T cells. II. A requirement for glycoprotein synthesis in virus-infected target cells.

Infection of cells with either ectromelia or lymphocytic choriomeningitis (LCM) virus in the presence of 2-deoxy-D-glucose (2-DOG) inhibited by up to 70% the extent to which the infected cells become susceptible to virus-specific cell-mediated lysis. The concentration of 2-DOG used had little effect on the extent of total protein synthesis (incorporation of [35S] methionine) but inhibited (up to 25%) glycoprotein synthesis, as measured by incorporation of [3H] fucose. This suggested that glycoprotein synthesis was a necessary event for infected cells to become susceptible to T-cell mediated lysis. The profiles (polyacrylamide gel electrophoresis) of newly synthesized, cellular glycoproteins from unifected and ectromelia-infected cells in the presence and absence of 2-DOG were compared and found to be very complex, with only minor changes. However, when convalescent serum from infected mice was used to isolate newly synthesized components from the cell surface shortly after infection, it showed four main species ranging in size from 25,000 to 70,000 daltons. 2-DOG inhibited production of these by 70%, thus corresponding to the biological data. The nature of the new glycoproteins seen in infected cells and whether they are in fact the structures recognized by effector T cells remain to be determined.

Antigens↗
PubMed1969

Cleavage of bacterial flagellin with cyanogen bromide. Chemical and physical properties of the protein fragments.

1. Flagellin, isolated from the flagella of Salmonella adelaide, was shown by various criteria to be a pure protein. It had a molecular weight of about 40000 and contained three methionine, six tyrosine, 11 arginine and 25 lysine residues/mol., of which 11 of the lysine residues were present as in-N-methyl-lysine. 2. After treatment of flagellin with cyanogen bromide in formic acid, four main fragments (A, B, C and D) were obtained, with as many as six minor components that represented partial degradation products. The major fragments were estimated by amino acid analysis to have molecular weights of about 18000 for fragment A, 12000 for fragment B, 5500 for fragment C and 4500 for fragment D. Fragments A, B and D, but not fragment C, were recovered pure by gel chromatography as monitored by polyacrylamide-gel electrophoresis. 3. A complex between fragments C and D was also isolated (mol.wt. 10000) after limited oxidation of flagellin by chloramine-t before digestion by cyanogen bromide. After oxidation essentially only two fragments were released from flagellin by cyanogen bromide: the ;C,D' complex and a presumed ;AB' fragment. 4. The sum of the amino acid analyses of fragments A and B and the ;C,D' complex gave residue values that agreed well with the amino acid composition of native flagellin. 5. Fragments A and D contained tyrosine, and ten of the 11 in-N-methyl-lysine residues of the molecule were in fragment A. Reaction with [(125)I]iodide at small extents of substitution showed that, in flagellin, the tyrosine residue of fragment D was more readily substituted than those of fragment A. By contrast, in polymerized flagellin, the tyrosine residues of fragment A were more readily substituted. 6. Treatment of flagellin with carboxypeptidases A and B revealed the C-terminal sequence -Leu-Leu-Leu-Arg. Arginine and leucine were released by carboxypeptidase from the ;C,D' complex but not from fragment D, indicating that fragment C was C-terminal. 7. On the basis of the results from amino acid analysis, carboxypeptidase digestion, N-terminal analysis, iodination studies and polyacrylamide-gel electrophoresis, the sequence of fragments in flagellin was considered to be B-A-D-C; in the polymer, fragment A was exposed. It is suggested that methylation of the lysine residues occurred in the organism after flagellin had polymerized.

Amino Acids↗
PubMed1969

Cleavage of bacterial flagellin with cyanogen bromide. Antigenic properties of the protein fragments.

1. Four polypeptide fragments, obtained by cyanogen bromide treatment of the protein flagellin from Salmonella adelaide, were tested for their antigenic activity by using them as inhibitors in three different assays: bacterial immobilization, haemagglutination of sensitized erythrocytes and quantitative micro precipitation. Immunodiffusion studies were also performed on the protein fragments. 2. Cleavage of the flagellin molecule in this way gave no detectable loss of antigenic determinants. Fragment A (mol.wt. 18000), the largest of the polypeptides, contained all the antigenic specificities present on flagellin that were recognized by the antisera used. In one test, fragment B (mol.wt. 12000) also contained antigenic activity to an extent not easily explainable by contamination with fragment A. Fragments C (mol.wt. 5500) and D (mol.wt. 4500) appeared to be antigenically inactive.

Antigens↗