ClpX Protein of Escherichia Coli Activates Bacteriophage Mu Transposase in the Strand Transfer Complex for Initiation of Mu DNA Synthesis

EMBO J. 1996 Feb 15;15(4):935-44.


During transposition bacteriophage Mu transposase (MuA) catalyzes the transfer of a DNA strand at each Mu end to target DNA and then remains tightly bound to the Mu ends. Initiation of Mu DNA replication on the resulting strand transfer complex (STC1) requires specific host replication proteins and host factors from two partially purified enzyme fractions designated Mu replication factors alpha and beta (MRFalpha and beta). Escherichia coli ClpX protein, a molecular chaperone, is a component required for MRFalpha activity, which removes MuA from DNA for the establishment of a Mu replication fork. ClpX protein alters the conformation of DNA-bound MuA and converts STC1 to a less stable form (STC2). One or more additional components of MRFalpha (MRFalpha2) displace MuA from STC2 to form a nucleoprotein complex (STC3), that requires the specific replication proteins and MRFbeta for Mu DNA synthesis. MuA present in STC2 is essential for its conversion to STC3. If MuA is removed from STC2, Mu DNA synthesis no longer requires MRFalpha2, MRFbeta and the specific replication proteins. These results indicate that ClpX protein activates MuA in STC1 so that it can recruit crucial host factors needed to initiate Mu DNA synthesis by specific replication enzymes.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATPases Associated with Diverse Cellular Activities
  • Adenosine Triphosphatases / physiology*
  • Bacteriophage mu / genetics*
  • Carrier Proteins / metabolism
  • DNA Nucleotidyltransferases / metabolism*
  • DNA Replication*
  • DNA, Viral / biosynthesis
  • Endopeptidase Clp
  • Escherichia coli / genetics
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial*
  • Gene Expression Regulation, Viral*
  • Integration Host Factors
  • Macromolecular Substances
  • Molecular Chaperones / metabolism
  • Transposases
  • Virus Replication*


  • Carrier Proteins
  • DNA, Viral
  • Escherichia coli Proteins
  • Integration Host Factors
  • Macromolecular Substances
  • Molecular Chaperones
  • integration host factor, E coli
  • DNA Nucleotidyltransferases
  • Transposases
  • Endopeptidase Clp
  • Adenosine Triphosphatases
  • ClpX protein, E coli
  • ATPases Associated with Diverse Cellular Activities