Temperature-sensitive mutations in the bacteriophage Mu c repressor locate a 63-amino-acid DNA-binding domain

Academic Article


  • Phage Mu's c gene product is a cooperative regulatory protein that binds to a large, complex, tripartite 184-bp operator. To probe the mechanism of repressor action, we isolated and characterized 13 phage mutants that cause Mu to undergo lytic development when cells are shifted from 30 to 42 °C. This collection contained only four mutations in the repressor gene, and all were clustered near the N terminus. The cts62 substitution of R47→Q caused weakened specific DNA recognition and altered cooperativity in vitro. A functional repressor with only 63 amino acids of Mu repressor fused to a C-terminal fragment of β-galactosidase was constructed. This chimeric protein was an efficient repressor, as it bound specifically to Mu operator DNA in vitro and its expression conferred Mu immunity in vivo. A DNA looping model is proposed to explain regulation of the tripartite operator site and the highly cooperative nature of repressor binding.
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    Digital Object Identifier (doi)

    Author List

  • Vogel JL; Li ZJ; Howe MM; Toussaint A; Higgins NP
  • Start Page

  • 6568
  • End Page

  • 6577
  • Volume

  • 173
  • Issue

  • 20