• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of pnasPNASInfo for AuthorsSubscriptionsAboutThis Article
Proc Natl Acad Sci U S A. Aug 1977; 74(8): 3292–3296.
PMCID: PMC431535

Binding of synthetic lactose operator DNAs to lactose repressors*


The nitrocellulose filter assay was used to study the interactions of wild-type (SQ) and tight-binding (QX86) lac repressors with synthetic lac operators 21 and 26 base pairs long. The repressor binding properties of both operators were very similar, indicating that both contain the same specific repressor recognition sites. The repressor-operator association rate constants (ka) were more sensitive than dissociation rate constants (kd) to changes in ionic strength. The responses of both ka and kd to ionic strength were relatively small compared to the effects previously observed with λh80dlac as operator DNA. These results suggest that under natural conditions there are electrostatic interactions between lac repressor and DNA regions outside of the 26 base pair operator sequence. Association rate constants for SQ repressor with either operator are higher than have been predicted for diffusion-limited reactions. We postulate that long-range electrostatic attractions between repressor and operator accelerate the association reaction. The presence of nonoperator DNA decreased association rate constants, the effect being more noticeable at an ionic strength of 0.05 M than at 0.20 M. Nonoperator DNA reduced ka values for associations involving QX86 repressor to a greater extent than for those with SQ repressor. The two types of repressors also had different rate constants for interactions with synthetic operators. The values for ka and kd were both higher with SQ repressor than with QX86 repressor. However, the rate constants were more sensitive to ionic strength when the repressor used was QX86.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.0M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Images in this article

Click on the image to see a larger version.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Beyreuther K, Adler K, Geisler N, Klemm A. The amino-acid sequence of lac repressor. Proc Natl Acad Sci U S A. 1973 Dec;70(12):3576–3580. [PMC free article] [PubMed]
  • Gilbert W, Maxam A. The nucleotide sequence of the lac operator. Proc Natl Acad Sci U S A. 1973 Dec;70(12):3581–3584. [PMC free article] [PubMed]
  • Dickson RC, Abelson J, Barnes WM, Reznikoff WS. Genetic regulation: the Lac control region. Science. 1975 Jan 10;187(4171):27–35. [PubMed]
  • Riggs AD, Suzuki H, Bourgeois S. Lac repressor-operator interaction. I. Equilibrium studies. J Mol Biol. 1970 Feb 28;48(1):67–83. [PubMed]
  • Riggs AD, Bourgeois S, Cohn M. The lac repressor-operator interaction. 3. Kinetic studies. J Mol Biol. 1970 Nov 14;53(3):401–417. [PubMed]
  • Goeddel DV, Yansura DG, Caruthers MH. Studies on gene control regions. 1. Chemical synthesis of lactose operator deoxyribonucleic acid segments. Biochemistry. 1977 May 3;16(9):1765–1772. [PubMed]
  • Yansura DG, Goeddel DV, Caruthers MH. Studies on gene control regions. 2. Enzymatic joining of chemically synthesized lactose operator deoxyribonucleic acid segments. Biochemistry. 1977 May 3;16(9):1772–1780. [PubMed]
  • Yansura DG, Goeddel DV, Cribbs DL, Caruthers MH. Studies of gene control regions. III. Binding of synthetic and modified synthetic lac operator DNAs to lactose repressor. Nucleic Acids Res. 1977 Mar;4(3):723–737. [PMC free article] [PubMed]
  • Maxam AM, Gilbert W. A new method for sequencing DNA. Proc Natl Acad Sci U S A. 1977 Feb;74(2):560–564. [PMC free article] [PubMed]
  • Betz JL, Sadler JR. Tight-binding repressors of the lactose operon. J Mol Biol. 1976 Aug 5;105(2):293–319. [PubMed]
  • Maniatis T, Jeffrey A, van deSande H. Chain length determination of small double- and single-stranded DNA molecules by polyacrylamide gel electrophoresis. Biochemistry. 1975 Aug 26;14(17):3787–3794. [PubMed]
  • Jobe A, Sadler JR, Bourgeois S. lac Repressor-operator interaction. IX. The binding of lac repressor to operators containing Oc mutations. J Mol Biol. 1974 May 15;85(2):231–248. [PubMed]
  • Jobe A, Bourgeois S. The lac repressor-operator interaction. VII. A repressor with unique binding properties: the X86 repressor. J Mol Biol. 1972 Dec 14;72(1):139–152. [PubMed]
  • Pfahl M. lac Repressor-operator interaction. Analysis of the X86 repressor mutant. J Mol Biol. 1976 Sep 25;106(3):857–869. [PubMed]
  • Itakura K, Katagiri N, Narang SA, Bahl CP, Marians KJ, Wu R. Chemical synthesis and sequence studies of deoxyribooligonucleotides which constitute the duplex sequence of the lactose operator of Escherichia coli. J Biol Chem. 1975 Jun 25;250(12):4592–4600. [PubMed]
  • Bahl CP, Wu R, Itakura K, Katagiri N, Narang SA. Chemical and enzymatic synthesis of lactose operator of Escherichia coli and its binding to lactose repressor. Proc Natl Acad Sci U S A. 1976 Jan;73(1):91–94. [PMC free article] [PubMed]
  • Bahl CP, Wu R, Stawinsky J, Narang SA. Minimal length of the lactose operator sequence for the specific recognition by the lactose repressor. Proc Natl Acad Sci U S A. 1977 Mar;74(3):966–970. [PMC free article] [PubMed]
  • Record MT, Jr, Lohman ML, De Haseth P. Ion effects on ligand-nucleic acid interactions. J Mol Biol. 1976 Oct 25;107(2):145–158. [PubMed]
  • Richter PH, Eigen M. Diffusion controlled reaction rates in spheroidal geometry. Application to repressor--operator association and membrane bound enzymes. Biophys Chem. 1974 Oct;2(3):255–263. [PubMed]
  • Berg OG, Blomberg C. Association kinetics with coupled diffusional flows. Special application to the lac repressor--operator system. Biophys Chem. 1976 Jul;4(4):367–381. [PubMed]
  • Lin SY, Riggs AD. Lac repressor binding to non-operator DNA: detailed studies and a comparison of eequilibrium and rate competition methods. J Mol Biol. 1972 Dec 30;72(3):671–690. [PubMed]
  • Lin S, Riggs AD. The general affinity of lac repressor for E. coli DNA: implications for gene regulation in procaryotes and eucaryotes. Cell. 1975 Feb;4(2):107–111. [PubMed]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


  • PubMed
    PubMed citations for these articles

Recent Activity

    Your browsing activity is empty.

    Activity recording is turned off.

    Turn recording back on

    See more...