| 1. |
- Bergqvist, A, et al.
(författare)
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Loss of DNA-binding and new transcriptional trans-activation function in polyomavirus large T-antigen with mutation of zinc finger motif.
- 1990
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Ingår i: Nucleic Acids Research. - 0305-1048 .- 1362-4962. ; 18:9, s. 2715-20
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Tidskriftsartikel (refereegranskat)abstract
- A putative zinc finger in polyomavirus large T-antigen was investigated. We were unable to demonstrate unequivocally a requirement for zinc in specific DNA-binding using the chelating agent 1, 10-phenanthroline. An involvement of the putative zinc finger in specific DNA-binding was nevertheless suggested by the properties of a mutant protein with a cys----ser replacement in the finger motif. Probably as a result of the defective DNA-binding, the mutant protein had lost its activity in initiation of viral DNA-replication and in negative regulation of viral early transcription. However, the trans-activation of the viral late promoter was normal. The analysis also revealed a previously unrecognized activity of large T-antigen. The mutant protein trans-activated the viral early promoter. In the wild-type protein this activity is probably concealed by the separate, negative regulatory function.
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| 2. |
- Bondeson, K, et al.
(författare)
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Lactose repressor-operator DNA interactions : kinetic analysis by a surface plasmon resonance biosensor.
- 1993
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Ingår i: Analytical Biochemistry. - 0003-2697 .- 1096-0309. ; 214:1, s. 245-51
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Tidskriftsartikel (refereegranskat)abstract
- Lactose repressor binding to operator DNA and subsequent dissociation of the complex was monitored continuously by a biosensor, measuring surface plasmon resonance. In this analysis a synthetic, double-stranded oligonucleotide containing the operator site was immobilized on the sensor surface and repressor protein was passed over the surface. The formation of the repressor-operator complex was specific and could be inhibited by isopropyl-beta-D-thiogalactopyranoside inducer. From the association curve, the apparent kass was determined to be 1.8 x 10(6) M-1 s-1. Dissociation of the complex was, for the first time for the lac repressor, determined as an uncatalyzed reaction and the kdiss was determined to be 3.4 x 10(-4) s-1. As a reference, the repressor-operator interaction was analyzed by electrophoretic mobility shift assay under similar reaction conditions. With this method the equilibrium binding constant was calculated to be 2.4 (+/- 0.2) x 10(8) M-1. The corresponding value calculated from biosensor data was 5.1 x 10(9) M-1.
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