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C F Wei

Publications and source records attributed to C F Wei.

49 records · Page 3Linked to original sources
PubMed1985

Molecular cloning and expression of partial cDNAs and deduced amino acid sequence of a carboxyl-terminal fragment of human apolipoprotein B-100.

Apolipoprotein (apo) B-100 cDNAs were identified in a human liver cDNA library cloned in the expression vector lambda gt11. The beta-galactosidase-apoB-100 fusion protein was detected by two independently produced low density lipoprotein polyclonal antisera and by three apoB-100 monoclonal antibodies that crossreact with apoB-74. It was not recognized by two apoB-100 monoclonal antibodies that crossreact with apoB-26. The longest clone, lambda B8, was completely sequenced. It contains a 2.8-kilobase DNA fragment containing the codons for the carboxyl-terminal 836 amino acid residues of apo-B-100, as well as the 3' untranslated region of apoB-100 mRNA. We have thus mapped apoB-74 to the carboxyl-terminal portion of apoB-100. The deduced amino acid sequence of the cloned DNA matches the sequences of 14 apoB-100 peptides determined in our laboratory. Minor differences in amino acid sequence were noted in three of the peptides, suggesting polymorphism of apoB-100 at the protein and DNA levels. Secondary structure predictions reveal an unusual pattern for apolipoproteins, consisting of beta-structure (24%), alpha-helical content (33%), and random structure (30%). Ten amphipathic helical regions of 10-24 residues were identified. This carboxyl-terminal fragment of apoB-100 is considerably more hydrophobic than other apolipoproteins with known structure. Its lipid binding regions might include stretches of highly hydrophobic beta-sheets as well as amphipathic helices. Our findings on apoB structure might be important for understanding the role of apoB-100-containing lipoproteins in atherosclerosis.

Amino Acid Sequence↗
PubMed1984

Terminally directed hydrolysis of duplex ribonucleic acid catalyzed by a species of the BAL 31 nuclease from Alteromonas espejiana.

The extracellular nuclease activities of Alteromonas espejiana sp. BAL 31 are mediated by at least two distinct protein species that differ in molecular weights and catalytic properties. The two species that have been purified to homogeneity and characterized, the "fast" (F) and "slow" (S) enzymes, both possess an exonuclease activity that shortens both strands of duplex DNA, with the F nuclease displaying a much greater (approximately 19-fold) turnover number for this degradation than the S species. In the present article, it is shown that the F species also mediates the terminally directed hydrolysis of a linear duplex RNA, gradually shortening molecules of this substrate through a mechanism that results in the removal of nucleotides from both the 3' and the 5' ends. This degradation proceeds with very infrequent introduction of scissions away from the termini as demonstrated by gel electrophoretic examination of the products of partial degradation, both in duplex form and after denaturation by reaction with CH3HgOH, and by electron microscopic characterization of duplex partially degraded molecules. The apparent Michaelis constant and turnover number have been determined. At equimolar enzyme concentrations in the limit of high substrate concentration, the F nuclease will degrade duplex RNA at a rate 0.021 +/- 0.010 (S.D.) times that for a duplex DNA of comparable guanine + cytosine content. The S species, by contrast, shows very little activity against the duplex RNA substrate relative to that of the F enzyme.

Endodeoxyribonucleases↗
PubMed1984

A single apurinic site can elicit BAL 31 nuclease-catalyzed cleavage in duplex DNA.

The extracellular nuclease from Alteromonas espejiana BAL 31 is a highly sensitive endonucleolytic probe for lesions that distort the helical structure of duplex DNA. The nuclease can be isolated as two distinct molecular species, the 'fast' (F) and 'slow' (S) species, which have different kinetic properties. When nonsupercoiled, covalently closed circular phage PM2 DNA containing apurinic sites introduced by heating at acid pH was incubated with individual fractions from a chromatographic column which separated the two nuclease species, cleavage of the DNA was observed which was greatly in excess of control levels using nonmodified DNA. The initial rates of such cleavage clearly paralleled the peaks of both absorbance and nuclease activity against single-stranded and linear duplex substrates. When samples of apurinic DNA were incubated with pooled fractions from the same column representing pure F and S nucleases, respectively, the rate and extent of the cleavage observed was dependent upon the average number of apurinic sites per molecule. Cleavage was readily detectable in samples containing an average of 1.1 apurinic sites per molecule with both species of the enzyme. These results indicate that either species of the BAL 31 nuclease can recognize and cleave in response to a single apurinic site in duplex DNA. The F nuclease appears to be approx. 2.5-times as efficient in cleaving DNA containing apurinic lesions as the S enzyme in extended incubations.

Apurinic Acid↗
PubMed1983

Isolation and comparison of two molecular species of the BAL 31 nuclease from Alteromonas espejiana with distinct kinetic properties.

The extracellular nuclease from Alteromonas espejiana sp. BAL 31 can be isolated as two distinct proteins, the "fast" (F) and "slow" (S) species, both of which have been purified to homogeneity. The F and S species of the nuclease have molecular weights, respectively, of 109 X 10(3) and 85 X 10(3), and both are single polypeptide chains with an isoelectric pH near 4.2. Both species catalyze the degradation of single-stranded and linear duplex DNAs to 5'-mononucleotides. The degradation of linear duplex DNA occurs through a terminally directed hydrolysis mechanism that results in the removal of nucleotides from both the 3' and 5' ends. Apparent Michaelis constants (Km) have been obtained for the exonuclease activities of both species and for the activity against single-stranded DNA of the S species. The Km for the hydrolysis of single-stranded DNA catalyzed by the F species has not been obtained because the reaction velocity was maximal even at the lowest substrate concentrations accessible in the photometric assay. The ratio of the turnover numbers for the exonuclease activities of the two species indicates that the F species will shorten linear duplex DNA at a rate 27 +/- 5 (S.D.) times faster than an equimolar concentration of the S species in the limit of high substrate concentration, while the corresponding ratio for the activities against single-stranded DNA (1.2 +/- 0.1) shows that the two species are similar with respect to hydrolysis of this substrate. In the limit of high substrate concentrations, the F and S species break phosphodiester bonds in single-stranded DNA at rates 1.3 +/- 0.3 and 33 +/- 2 times those for the exonucleolytic degradation of linear duplex DNA, respectively. It has not been established whether the two species are physically related.

Bacteria↗
PubMed1983

BAL 31 nuclease as a probe in concentrated salt for the B-Z DNA junction.

The BAL 31 nuclease, an extracellular nuclease from A. espejiana, specifically recognizes and cleaves the salt induced conformational junction between B and Z-DNA. Short segments of (dC-dG) left-handed Z-helix, comprising approximately 1% of the total DNA, are specifically detected within two different recombinant plasmids. The BAL 31 enzyme is highly resistant to inactivation by the presence of high concentrations of a variety of electrolytes that stabilize left-handed helices, is active at physiological pH, and can be used to probe both linear and circular DNAs. Additionally, the nuclease cleaves left-handed (dC-dG)n only very poorly, if at all. Thus, the BAL 31 nuclease can be utilized as a probe for helical junctions and consequently for segments of left-handed DNA that might exist within predominantly right-handed naturally occurring genomes.

Bacteria↗
PubMed1982

[Clinical experience in systemic lupus erythematosus (author's transl)].

Thirty-four cases of SLE treated during the past seven years (1974-1981) in Taipei Municipal Jen-Ai Hospital are reported and analyzed. Diagnosis of SLE was based on ARA preliminary criteria and Hahn's preliminary criteria. There were 32 females (94.2%) and 2 males (5.8%). The mean age at diagnosis was 28.5 years (range 14-51). Clinical manifestations were as follows: facial erythema 24 cases (70.6%), Raynaud's phenomenon 4 cases (11.4%), oral or nasopharyngeal ulceration 7 cases (20.6%), arthritis without deformity 22 cases (64.7%), proteinuria 21 cases (61.8%), pleural or pericardial effusions 13 cases (38.2%), psychosis or convulsions 9 cases (26.5%), hematological abnormalities 25 cases (73.5%). Laboratory findings were as follows: positive ANA test 33/34 (97.0%), hypocomplementemia 10/13 (76.9%), direct Coombs' test 4/18 (22.2%), indirect Coombs' test 1/13 (7.6%), LE cell 19/34 (55.9%), RA Latex 7/17 (41.7%), polyclonal gammopathy 15/17 (88.2%), anemia 25/34 (73.5%), leukopenia 12/34 (35.3%), thrombocytopenia 10/34 (29.4%). Three cases were complicated by herpes zoster, one by hyperthyroidism, and one by autoimmune thyroiditis. Ten cases died, including 4 renal failure, 2 heart failure, 2 cases of committed suicide and 1 case of CNS involvement.

Adolescent↗
PubMed1981

Type I DNA topoisomerases from mammalian cell nuclei interlock strains and promote renaturation of denatured closed circular PM2 DNA.

Type I DNA topoisomerases from mouse ascites cell nuclei and from rat liver cell nuclei act on denatured viral closed circular PM2 DNA to produce molecules with a highly contracted structure as well as fully duplex non-supercoiled covalently closed circular molecules. Highly contracted DNA molecules contain a novel type of topological linkage in which a strand in one region of the double-stranded molecule passes between the strands in another region of the circular molecule one or more times. Since it is also found that the action of the topoisomerase promotes renaturation of complementary strands in denatured closed circular DNA, it is suggested that formation of contracted DNA structures proceeds through renatured, duplex intermediates with highly negative superhelix densities that contain small single-stranded regions.

Animals↗
PubMedDate not supplied

Germ cell tumor in infancy and childhood: experience at one institute compared to other studies.

To understand the difference in incidence and distribution of germ cell tumor (GCT) between cases seen in this institute and Western studies, 98 cases of GCTs collected from 1979 to 1996 were included 50 with gonadal GCTs, 9 with mediastinal GCTs; 9 with retroperitoneal GCTs, 10 with sacrococcygeal GCTs and 20 with intracranial GCTs; all were analyzed retrospectively by chart review. The incidences of testicular and intracranial GCT in all GCTs were higher in this study, i.e. 26.5%(26/98) and 20.4%(20/98) compared to 7% and 6% of American reports. But the incidence of sacrococcygeal GCT in all GCTs was lower in this study, i.e. 10.2%(10/98) compared to 41% of American reports. The incidences of testicular and ovarian GCT in all GCTs were about the same in this study, i.e. 26.5%(26/98) and 24.5%(24/98) compared to 7% and 29% of American reports; 51%(50/98) of all GCTs were gonadal in this study compared to 36% in the American reports.

Adolescent↗