Role of hydration in the binding of lac repressor to DNA

Michael G. Fried, Douglas F. Stickle, Karen Vossen Smirnakis, Claire Adams, Douglas MacDonald, Ponzy Lu

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


The osmotic stress technique was used to measure changes in macromolecular hydration that accompany binding of wild-type Escherichia coli lactose (lac) repressor to its regulatory site (operator O1) in the lac promoter and its transfer from site O1 to nonspecific DNA. Binding at O1 is accompanied by the net release of 260 ± 32 water molecules. If all are released from macromolecular surfaces, this result is consistent with a net reduction of solvent-accessible surface area of 2370 ± 550 Å2. This area is only slightly smaller than the macromolecular interface calculated for a crystalline repressor dimer-O1 complex but is significantly smaller than that for the corresponding complex with the symmetrical optimized Osym operator. The transfer of repressor from site O1 to nonspecific DNA is accompanied by the net uptake of 93 ± 10 water molecules. Together these results imply that formation of a nonspecific complex is accompanied by the net release of 165 ± 43 water molecules. The enhanced stabilities of repressor-DNA complexes with increasing osmolality may contribute to the ability of Escherichia coli cells to tolerate dehydration and/or high external salt concentrations.

Original languageEnglish
Pages (from-to)50676-50682
Number of pages7
JournalJournal of Biological Chemistry
Issue number52
StatePublished - Dec 27 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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