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DNA-Binding Activity of the Streptococcus thermophilus Phage Sfi21 Repressor

Bruttin, Anne; Foley, Sophie; Br�ssow, Harald


Anne Bruttin

Harald Br�ssow


The cloned Streptococcus thermophilus phage Sfi21 repressor open reading frame (orf) 127 gp protects a cell against superinfection with the homologous temperate, but not against virulent phages. As demonstrated by DNase protection assay and gel shift experiments, the repressor binds to a 25-bp operator site located upstream of the repressor gene. A second sequence-related operator was identified 265 bp apart at the 3′-end of orf 75, the topological equivalent of a cro repressor gene. The replacement of a bp at the middle or at the right side of the operator decreased substantially the affinity of the repressor for the operator. In gel shift assays, the 75 gp did not bind DNA from the genetic switch region. However, when increasing amounts of orf 75 gp containing cell extracts were added to orf 127 gp containing cell extracts, the repressor could no longer bind its operator site.

Journal Article Type Article
Acceptance Date May 14, 2002
Publication Date 2002-11
Deposit Date Jul 14, 2008
Journal Virology
Print ISSN 0042-6822
Electronic ISSN 1096-0341
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 303
Issue 1
Pages 100-109
Keywords Streptococcus thermophilus phage Sfi21 repressor; DNA binding; Binding sites; Binding suppression;
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