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Biomedical subjects

W G Lewis

Publications and source records attributed to W G Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1985

c-erbB activation in avian leukosis virus-induced erythroblastosis: clustered integration sites and the arrangement of provirus in the c-erbB alleles.

There is considerable evidence that links the activation of cellular genes to oncogenesis. We previously reported that structural rearrangements in the cellular oncogene c-erbB correlate with the development of erythroblastosis induced by avian leukosis virus (ALV). c-erbB recently has been shown to be related to the gene encoding epidermal growth factor receptor. We now have characterized the detailed mechanisms of c-erbB activation by ALV proviruses. We report here that the ALV proviral integration sites are clustered 5' to the region where homology to v-erbB starts, suggesting that interruption in this region of c-erbB is important for its activation. The proviruses are oriented in the same transcriptional direction as c-erbB and usually are full-size. The latter finding is in contrast to the frequent deletions observed within the c-myc-linked proviruses in B-cell lymphomas. We have also identified a second c-erbB allele, which differs from the previously known allele primarily by a deletion in an intron region. This allele is also oncogenic upon mutation by an ALV provirus.

Alleles↗
PubMed1983

The amino acid sequence of human liver apoferritin.

The protein component of the iron storage molecule, ferritin, contains 24 subunits in form of a hollow shell known as apoferritin. The amino acid sequence has been determined for apoferritin subunits from human liver. The sequence comprises 174 amino acids giving an Mr of 19 900. It shows extensive homology with the primary structures of apoferritins from human and horse spleen and from rat liver. Sequence substitutions are discussed in relation to the known three-dimensional structure of horse spleen apoferritin. Evidence for a second minor sequence in human liver apoferritin is presented.

Amino Acid Sequence↗
PubMed1983

Amino acid sequence of equine platelet tropomyosin. Correlation with interaction properties.

Equine platelet beta tropomyosin (247 residues), like rabbit skeletal muscle alpha tropomyosin (284 residues) has a repeating pattern of amino acid residues characteristic of a coiled-coil structure. When compared with the muscle protein, it is extended by 5 residues at the NH2-terminus and possesses two 21 residue deletions (positions 23-43 and 60-80 of the muscle sequence). The two proteins are highly conserved from residues 81-260, but are significantly different at their COOH-termini (residues 261-284). These differences in platelet tropomyosin can be correlated with its diminished head-to-tail polymerization, a weaker interaction with F-actin and a reduced affinity for muscle troponin and the T1 fragment of troponin-T.

Amino Acid Sequence↗
PubMed1983

Activation of the cellular oncogene c-erbB by LTR insertion: molecular basis for induction of erythroblastosis by avian leukosis virus.

Avian leukosis virus (ALV), a slowly oncogenic retrovirus, induces in chickens a variety of neoplasms, including lymphoid leukosis and erythroblastosis. In lymphoid leukosis, a cellular oncogene, c-myc, is activated by the insertion of ALV LTR. We provide evidence that ALV utilizes a similar mechanism in erythroblastosis induction by activating a different cellular oncogene, c-erbB. We report the isolation, from leukemic erythroblast DNA, of a clone that represents the viral-cell junction fragment and carried the ALV LTR and part of the c-erbB locus. Restriction and sequence analyses reveal that the LTR is located upstream from the erbB coding region and is oriented in the same transcriptional direction; such a structure would be compatible with the promoter-insertion type of activation. Our findings provide a molecular explanation for the multipotency of slowly oncogenic retroviruses.

Animals↗
PubMed1982

Enzymatic sulfation of steroids. XV. Studies differentiating between rat liver androgen, estrogen, bile acid, glucocorticoid and phenol sulfotransferases.

Earlier reports left the number of enzymes that catalyzed phenol, androgen, estrogen, bile acid and glucocorticoid sulfation obscure. Here, we have utilized chromatographic, immunochemical and endocrinologic methods to compare and differentiate these enzymes in rat liver. Sulfotransferases I, II, and III--which sulfate glucocorticoids--were used in this comparison. We found that phenols were sulfated by phenol sulfotransferases 1 and 2, which were unrelated to the other enzymes studied here. Large amounts of phenol sulfotransferase 1 were found in both sexes. Large amounts of phenol sulfotransferase 2 were restricted to males. By contrast, the small amount of androgen sulfation found in both sexes appeared to be mediated by sulfotransferase II, which preferred 3 beta-hydroxysteroids, but also sulfated estrogens and glucocorticoids to lesser extents. The sulfation of estrogens presented a more complex picture. Most estradiol sulfotransferase activity in both sexes was due to an enzyme that sulfated estrone poorly, and did not sulfate the other steroids tested. This specific estradiol sulfotransferase was unrelated to the other sulfotransferases described here. Smaller amounts of estrogen sulfotransferase activity that sulfated estradiol and estrone equally well were present at concentrations dependent on the sex of test animals. This enzyme activity appeared to be due to sulfotransferases I, II and III. Most bile acid sulfotransferase activity eluted from DEAE-Sephadex A-50 columns with sulfotransferases I and II. However, data with males suggested that these enzymes were not responsible. Thus, phenols, androgens, estrogens and glucocorticoids were sulfated by six enzymes of differing substrate specificity: phenol sulfotransferases 1 and 2, specific estradiol sulfotransferase, and sulfotransferases I, II, and III. Unique bile acid sulfotransferases also appeared probable.

Adrenalectomy↗
PubMed1980

The amino acid sequence of rabbit cardiac tropomyosin.

The amino acid sequence of rabbit cardiac tropomyosin has been investigated by the isolation of peptides derives from cyanogen bromide and proteolytic degradations. Based on identical amino acid compositions, electrophoretic mobilities, and in some cases, NH2-terminal analyses, all peptides were shown to be the same as peptides in the amino acid sequence of rabbit skeletal alpha-tropomyosin. The apparent heterogeneity of the cardiac protein previously observed on alkaline-urea polyacrylamide electrophoresis gels is attributable to a phosphorylated species. We conclude that the primary structures of the cardiac and skeletal alpha component are identical. Differences in actin-linked calcium regulation in skeletal and cardiac muscle must reside largely in the troponin components.

Alkaline Phosphatase↗
PubMed1978

Specificity and inhibition studies of Armillaria mellea protease.

The action of Armillaria mellea protease has been evaluated on a number of polypeptide substrates. It has been shown to split the Pro7-Lys8 bonds in both native and oxidised lysine-vasopressin and the Ser11-Lys12 bond in glucagon. No other splits were detected in these substrates. The enzyme also caused extensive degradation of S-carboxymethyl lysozyme, S-carcoxymethyl pepsinogen and oxidised ribonuclease. A. In each case the only new amino-terminal residue to appear was lysine. A. mellea protease was inhibited by the chelating agents 1,10-phenanthroline, alpha, alpha'-bipyridine and imidazole. The pK1 values (negative log10 of concentration required for 50% inhibition) for these three inhibitors were 3.9, 3.4 and 1.1, respectively. Lysine, S-2-aminoethylcysteine and short chain aliphatic amines also proved to be relatively good inhibitors of A. mellea protease while arginine was a poor inhibitor.

Amines↗