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Differential role of the Mu B protein in phage Mu integration vs. replication: mechanistic insights into two transposition pathways
Author(s) -
Roldan Leslie Ann S.,
Baker Tania A.
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02364.x
Subject(s) - transposase , bacteriophage mu , biology , mutant , transposition (logic) , microbiology and biotechnology , dna replication , transposable element , dna , genetics , gene , linguistics , philosophy
The Mu B protein is an ATP‐dependent DNA‐binding protein and an allosteric activator of the Mu transposase. As a result of these activities, Mu B is instrumental in efficient transposition and target‐site choice. We analysed in vivo the role of Mu B in the two different recombination reactions performed by phage Mu: non‐replicative transposition, the pathway used during integration, and replicative transposition, the pathway used during lytic growth. Utilizing a sensitive PCR‐based assay for Mu transposition, we found that Mu B is not required for integration, but enhances the rate and extent of the process. Furthermore, three different mutant versions of Mu B, Mu B C99Y , Mu B K106A , and Mu B 1−294 , stimulate integration to a similar level as the wild‐type protein. In contrast, these mutant proteins fail to support Mu growth. This deficiency is attributable to a defect in formation of an essential intermediate for replicative transposition. Biochemical analysis of the Mu B mutant proteins reveals common features: the mutants retain the ability to stimulate transposase, but are defective in DNA binding and target DNA delivery. These data indicate that activation of transposase by Mu B is sufficient for robust non‐replicative transposition. Efficient replicative transposition, however, demands that the Mu B protein not only activate transposase, but also bind and deliver the target DNA.