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61.
Purification and characterization of yeast topoisomerase I 总被引:2,自引:0,他引:2
G Badaracco P Plevani W T Ruyechan L M Chang 《The Journal of biological chemistry》1983,258(3):2022-2026
Yeast topoisomerase I (Mr = 76,000) has been purified to 80% homogeneity using a combination of ion exchange, gel filtration, and DNA-cellulose chromatography. The enzyme was characterized with respect to its ability to relax supercoiled DNA and to catenate nicked circular DNA. Yeast topoisomerase I will remove both positive and negative turns in DNA supercoils in the absence of ATP and magnesium ion. The products of the catenating activity of the enzyme were examined on agarose gels and in the electron microscope. These analyses indicate that yeast topoisomerase I will generate large catenated DNA networks which appear to rearrange to multimeric linear structures upon long incubation time. 相似文献
62.
G Badaracco L Capucci P Plevani L M Chang 《The Journal of biological chemistry》1983,258(17):10720-10726
DNA polymerase I of the yeast Saccharomyces cerevisiae has been purified to near homogeneity. The enzyme sediments under high salt conditions as a band at 7.4 S and two polypeptides of Mr = 140,000 and 110,000 are resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Both polypeptides react with rabbit anti-yeast DNA polymerase I serum and can be shown to be enzymatically active by renaturation in situ after electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate. This high molecular weight form of yeast DNA polymerase I is very sensitive to inhibition by aphidicolin. The biochemical properties of the enzyme and inhibitors that may aid in distinguishing yeast DNA polymerases I and II are also described. 相似文献
63.
The interaction between deoxyguanosine (dG) and cis-dichlorodiammineplatinum(II) (cis-Pt) leads to the 2:1 and the 1:1 dG-Pt adducts. These adducts were separated on an Aminex A6 cationexchange column by use ot 0.01 M K2CO3 (pH 11) as an eluent. The stoichiometry of the adducts was determined from the 195mPt radioactivity and from the absorbance of the guanine chromophore at 280 nm. Time-course studies show that dG reacts initially with cis-Pt to form the 1:1 adduct, which then interacts with a second molecule of dG to form the 2:1 adduct. Acid hydrolysis (100°C in 88% formic acid for 5–15 min) of the 1:1 and 2:1 adducts results in their conversion to two new products, which elute differently from the column but which still contain Pt bound in the same stoichiometric ratio to dG as in the nonhydrolyzed adducts. The hydrolyzed adducts show a negative diphenylamine reaction indicative ot cleavage of the glycosidic bond. It is concluded that mild acid hydrolysis converts the 1:1 and 2:1 dG-Pt adducts into the corresponding guanine-Pt adducts, which are chromatographically distinguishable. This acid hydrolysis-high pressure liquid chromatography (HPLC) procedure has application to the identification of the Pt adducts formed in DNA. 相似文献
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Genetic and biochemical distinction among Chinese hamster cell emtA, emtB, and emtC mutants. 总被引:1,自引:1,他引:0 下载免费PDF全文
Genetic and biochemical experiments have enabled us to more clearly distinguish three genetic loci, emtA, emtB, and emtC, all of which can be altered to give rise to resistance to the protein synthesis inhibitor, emetine, in cultured Chinese hamster cells. Genetic experiments have demonstrated that, unlike the emtB locus, neither the emtA locus nor the emtC locus is linked to chromosome 2 in Chinese hamster cells, clearly distinguishing the latter two genes from emtB. emtA mutants can also be distinguished, biochemically, from emtB and emtC mutants based upon different degrees of cross-resistance to another inhibitor of protein synthesis, cryptopleurine. Two-dimensional gel electrophoretic analysis of ribosomal proteins failed to detect any electrophoretic alterations in ribosomal proteins from emtA or emtC mutants that could be correlated with emetine resistance. However, a distinct electrophoretic alteration in ribosomal protein S14 was observed in an emtB mutant. In addition, the parental Chinese hamster peritoneal cell line of an emtC mutant, and the emtC mutant itself, are apparently heterozygous for an electrophoretic alteration in ribosomal protein L9. 相似文献
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S H Chang S Kuo E Hawkins N R Miller 《Biochemical and biophysical research communications》1973,51(4):951-955
The nucleotide sequence of “Renaturable” leucine transfer RNA from Baker's yeast has been re-investigated. The results showed that (i) this tRNA has a sequence of DCD at positions 19–21, (ii) it has an anticodon m5CAA and (iii) it has a pseudouridine at position 40. 相似文献