Domains of Mnt repressor: roles in tetramer formation, protein stability, and operator DNA binding

Biochemistry. 1995 Oct 10;34(40):13109-16. doi: 10.1021/bi00040a023.


The Mnt repressor of bacteriophage P22 is a member of the ribbon-helix-helix family of gene regulatory proteins. Proteolytic cleavage of Mnt with chymotrypsin reveals that it consists of two structural domains. Both domains are required for high-affinity operator binding. The N domain (residues 1-51) is dimeric and binds weakly but specifically to operator DNA. The C domain (residues 52-82) forms an independent alpha-helical, tetramerization domain and, by itself, has no DNA-binding activity. In intact Mnt, the N and C domains help to stabilize each other against denaturation but appear to be linked rather flexibly. Assays of the half-operator affinities of Mnt and the isolated N domain indicate that binding to adjacent half-sites in the whole operator is stabilized by protein-protein contacts between N domains in addition to protein-protein contacts between C domains.

Publication types

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

MeSH terms

  • Allosteric Regulation
  • Amino Acid Sequence
  • Bacteriophage P22 / genetics*
  • Base Sequence
  • DNA-Binding Proteins / chemistry*
  • Macromolecular Substances
  • Molecular Sequence Data
  • Operator Regions, Genetic*
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Repressor Proteins / chemistry*
  • Structure-Activity Relationship
  • Viral Proteins / chemistry*
  • Viral Regulatory and Accessory Proteins


  • DNA-Binding Proteins
  • Macromolecular Substances
  • Repressor Proteins
  • Viral Proteins
  • Viral Regulatory and Accessory Proteins
  • phage repressor proteins