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141.
K S Park D H Sohn R L Veech B J Song 《Biochemical and biophysical research communications》1992,185(2):676-682
Pentoxyresorufin O-depentylase activity, mainly associated with phenobarbital-inducible cytochrome P450IIB1 (designated CYP2B1), was increased after a single treatment of pyridine (250 mg/kg, i.p.), and further increased by repeated treatments for 5 days. The catalytic activity and immunoreactive protein of CYP2B recognized by polyclonal antibodies were significantly induced by a relatively high dose of pyridine (250 mg/kg, i.p.) while ethanol-inducible cytochrome P450IIE1 (CYP2E1) could be induced by a low dosage (25 mg/kg, i.p.). Unlike CYP2E1 induction without changing its mRNA level, the induction of CYP2B by pyridine was accompanied by an elevation of its mRNA, indicating a pre-translational activation of this enzyme. These results indicate that pyridine induces various isozymes of cytochromes P450 by different induction mechanisms. 相似文献
142.
Although the icosahedral bacteriophage T7 capsid has a diameter (58 nm) that is 234-fold smaller than the length of the linear, double-stranded T7 DNA, binding of a T7 capsid to T7 DNA is found here to have dramatic effects on the migration of the DNA during both pulsed field agarose gel electrophoresis (PFGE; the field inversion mode is used) and constant field agarose gel electrophoresis (CFGE). For these studies, capsid-DNA complexes were obtained by expelling DNA from mature bacteriophage T7; this procedure yields DNA with capsids bound at a variable position on the DNA. When subjected to CFGE at 2-6 V/cm in 0.20-2.5% agarose gels, capsid-DNA complexes arrest at the electrophoretic origin. Progressively lowering the electrical potential gradient to 0.5 V/cm results in migration; most complexes form a single band. The elevated electrical potential gradient (3 V/cm) induced arrest of capsid-DNA complexes is reversed when PFGE is used instead of CFGE. For some conditions of PFGE, the mobility of capsid-DNA complexes is a function of the position of the capsid on the DNA. During either CFGE (0.5 V/cm) or PFGE, capsid-DNA complexes increasingly separate from capsid-free DNA as the percentage of agarose increases. During these studies, capsid-DNA complexes are identified by electron microscopy of enzymatically-digested pieces of agarose gel; this is apparently the first successful electron microscopy of DNA from an agarose gel.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
143.
Glutamate dehydrogenase (L-glutamate:NAD(P)+ oxidoreductase, deaminating, EC 1.4.1.3) from the hyperthermophilic Archeon Pyrococcus furiosus was purified to homogeneity by chromatography on anion-exchange, molecular-exclusion and hydrophobic-interaction media. The purified native enzyme had an M(r) of 270,000 +/- 15,000 and was shown to be a hexamer with identical subunits of M(r) 46,000. The enzyme was exceptionally thermostable, having a half-life of 3.5 to more than 10 h at 100 degrees C, depending on the concentration of enzyme. The Km of the enzyme for ammonia was high (9.5 mM), indicating that the enzyme is probably active in the deaminating, catabolic direction. The coenzyme utilization of the enzyme resembled the equivalent enzymes from eukaryotes rather than eubacteria, since both NADH and NADPH were recognized with high affinity. The enzyme displayed a preference for NADP+ over NAD+ that was more pronounced at low assay temperatures (50-70 degrees C) compared with the optimal temperature for enzyme activity, 95 degrees C. 相似文献
144.
Summary Fifteen strains of yeast, which produced an extracellular amylolytic enzymes, were isolated from nature. One of them produced more than 100 times the enzyme activity in comparison with the 14 strains and the extremely hyperproducing strain of yeast was identified asCandida
sp. 347. Paper chromatograms of the amylolytic enzyme demonstrated activity of amyloglucosidase. The optimum pH for activity of the enzyme was 5.5–6.0 and optimum temperature was 60°C. 相似文献
145.
J Salfeld H G Gttlinger R A Sia R E Park J G Sodroski W A Haseltine 《The EMBO journal》1990,9(3):965-970
A 26 kd protein reactive with antiserum to the transactivator tat of the Human Immunodeficiency Virus Type 1 (HIV-1) has been detected in virus producing cells. The 26 kd protein is shown to be a tripartite fusion protein including coding sequences of the tat, envelope (env) and regulator of virion expression (rev) genes. Fusion of these coding sequences occurs by use of a previously undescribed exon within env. This 26 kd protein, designated tnv, has tat but no rev activity detectable with the assay used. The existence of other less abundant tat and rev related proteins in HIV-1 producing cells is also noted. 相似文献
146.
Identification of the mpl gene encoding UDP-N-acetylmuramate: L-alanyl-gamma-D-glutamyl-meso-diaminopimelate ligase in Escherichia coli and its role in recycling of cell wall peptidoglycan.
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A gene, mpl, encoding UDP-N-acetylmuramate:L-alanyl-gamma-D-glutamyl-meso-diaminopimelat e ligase was recognized by its amino acid sequence homology with murC as the open reading frame yjfG present at 96 min on the Escherichia coli map. The existence of such an enzymatic activity was predicted from studies indicating that reutilization of the intact tripeptide L-alanyl-gamma-D-glutamyl-meso-diaminopimelate occurred and accounted for well over 30% of new cell wall synthesis. Murein tripeptide ligase activity could be demonstrated in crude extracts, and greatly increased activity was produced when the gene was cloned and expressed under control of the trc promoter. A null mutant totally lacked activity but was viable, showing that the enzyme is not essential for growth. 相似文献
147.
Dong-Uk Kim Seung-Kiel Park Kyung-Sook Chung Myung-Un Choi Hyang-Sook Yoo 《Molecular & general genetics : MGG》1996,252(1-2):20-32
ASchizosaccharomyces pombe homolog of mammalian genes encoding G protein subunits,gpb1
+, was cloned by the polymerase chain reaction using primer pairs that correspond to sequences conserved in several G genes of other species followed by screening of genomic and cDNA libraries. Thegpb1 gene encodes 317 amino acids that show 47% homology with human G
1 and G
2 and 40% homology withSaccharomyces cerevisiae G protein. Disruption of thegpb1 gene indicated that this gene is not required for vegetative cell growth. However,gpb1-disrupted haploid cells mated and sporulated faster than wild-type cells, both in sporulation (MEA) and in complex medium (YE): when examined 23 h after transfer to sporulation medium, 35% ofgpb1-disrupted haploid pairs had undergone conjugation and sporulation, whereas only 3–5% of wild-type haploid pairs had done so. Overexpression of thegpb1 gene suppressed this facilitated conjugation and sporulation phenotype ofgpb1-disrupted cells but did not cause any obvious effect in wild-type cells. Co-disruption of one of the twoS. pombe G-subunit genes,gpa2, in thegpb1-disrupted cells did not change the accelerated conjugation and sporulation phenotype of thegpb1
– cells. However, co-disruption of theras1 gene abolished thegpb1
– phenotype. These results suggest that Gpbl is a negative regulator of conjugation and sporulation that apparently works upstream of Ras1 function inS. pombe. The possible relationship of Gpbl to two previously identified, putative G proteins ofS. pombe is discussed.A preliminary report of this work first appeared in an abstract of the Genetic Society of America, 1993 Yeast Genetics and Molecular Biology Meeting, p. 92 and was presented at the American Association of Cancer special meeting on Cell Signalling and Cancer Treatment, 1993 相似文献
148.
Yeon-Jeong Kim Jong-Hoon Park Koung-Sook Kim Ji-Eun Chang Jeong Heon Ko Myung-Hee Kim Dong-Hyo Chung Tae-Wha Chung In-Seong Choe Young-Choon Lee Cheorl-Ho Kim 《Gene》1996,170(2):281-283
We have isolated and characterized the immediate (1651 bp) 5′-flanking region of the gene (GnT-III) encoding N-acetylglucosaminyltransferase III (GnT-III) from a human placental genomic library. Analysis of promoter elements shows a similarity to the 5′-flanking region of murine 1,4-galactosyltransferase. The sequence lacks obvious TATA elements and CCAAT boxes; however, putative regulatory sites, including 2 potential cAMP-response regulatory elements (CRE), 11 insulin-response element consensus sequences (IRE), 7 potential AP-2-binding sites, 2 SP1 consensus sequences (GC boxes) and 2 sequences similar to the half-palindromic glucocorticoid-responsive element (GRE), are present. 相似文献
149.
S. Igimi C.H. Ryu S.H. Park Y. Sasaki T. Sasaki S. Kumagai 《Letters in applied microbiology》1996,23(1):31-35
Conjugal transfer of plasmid pAMβ1 from Lactococcus lactis to intestinal bacteria of BALB/c mice was studied. Plasmid transfer was observed to Enterococcus faecalis in vitro by a filter mating method with transfer frequencies of 2.3 × 10−3 and with lower frequencies to other species. In vivo , using gastric intubation with the pAMβ1-bearing Lactococcus lactis as donor and Ent. faecalis as recipient, a few transconjugants were detected from faecal Ent. faecalis . However, when these mice were given erythromycin through drinking water, a large number of conjugated Ent. faecalis were detected in faeces. Plasmid transfer to Ent. faecalis occurred at high frequency, 1.2 × 10−3 , in mice whose anus was artificially closed after gastric intubation with pAMβ1-bearing Lactococcus lactis . These results demonstrate clearly that pAMβ1 transfer occurs between Gram-positive bacteria in the gut of mice harbouring many species of bacteria. 相似文献
150.
J.Y. Roh H.W. Park B.R. Jin H.S. Kim Y.M. Yu S.K. Kang 《Letters in applied microbiology》1996,23(4):249-252
J.Y. ROH, H.W. PARK, B.R. JIN, H.S. KIM, Y.M. YU AND S.K. KANG. 1996. Four Bacillus thuringiensis isolates from soil samples produced parasporal inclusions which were non-toxic to insects. The isolates were named B. thuringiensis NTB-1, NTB-2, NTB-3 and NTB-4. The parasporal inclusions were shown to be ovoid by phase contrast and scanning electron microscopy. The serotypes of the four isolates were determined by agglutination using 33 antisera; NTB-1 and NTB-4 seemed to be subsp. isruelensis ,and NTB-2 seemed to be subsp. pondzcheriensis . NTB-3 did not react with the 33 antisera. However, comparison of parasporal protein and plasmid DNA patterns of the four isolates with those of 15 known non-toxic B. thuringiensis strains demonstrated that the four isolates are novel. 相似文献