Crystal structure of a 1.6-hexanediol bound tetrameric form of Escherichia coli lac-repressor refined to 2.1 A resolution

Proteins. 2009 May 15;75(3):748-59. doi: 10.1002/prot.22284.


We report the structure of a novel tetrameric form of the lactose repressor (LacI) protein from Escherichia coli refined to 2.1 A resolution. The tetramer is bound to 1.6-hexanediol present in the crystallization solution and the final R(free) for the structure is 0.201. The structure confirms previously reported structures on the monomer level. However, the tetramer is much more densely packed. This adds a new level of complexity to the interpretation of mutational effects and challenges details in the current model for LacI function. Several amino acids, previously associated with changes in function but unexplained at the structural level, appear in a new structural context in this tetramer which provides new implications for their function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Computational Biology / methods
  • Crystallography, X-Ray
  • Escherichia coli / chemistry*
  • Escherichia coli Proteins / chemistry*
  • Glycols / chemistry*
  • Ligands
  • Models, Molecular
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Quaternary
  • Repressor Proteins / chemistry*
  • Spectrometry, Fluorescence


  • Escherichia coli Proteins
  • Glycols
  • Ligands
  • Repressor Proteins
  • hexamethylene glycol