Ikappa Balpha functions through direct contacts with the nuclear localization signals and the DNA binding sequences of NF-kappaB

J Biol Chem. 1998 Sep 25;273(39):25427-35. doi: 10.1074/jbc.273.39.25427.

Abstract

We have determined the binding energies of complexes formed between Ikappa Balpha and the wild type and mutational variants of three different Rel/NF-kappaB dimers, namely, the p50/p65 heterodimer and homodimers of p50 and p65. We show that although a common mode of interaction exists between the Rel/NF-kappaB dimers and Ikappa Balpha, IkappaB alpha binds the NF-kappaB p50/p65 heterodimer with 60- and 27-fold higher affinity than the p50 and p65 homodimers, respectively. Each of the three flexibly linked segments of the rel homology region of Rel/NF-kappaB proteins (the nuclear localization sequence, the dimerization domain, and the amino-terminal DNA binding domain) is directly engaged in forming the protein/protein interface with the ankyrin repeats and the carboxyl-terminal acidic tail/PEST sequence of Ikappa Balpha. In the cell, Ikappa Balpha functions to retain NF-kappaB in the cytoplasm and inhibit its DNA binding activity. These properties are a result of the direct involvement of the nuclear localization sequences and of the DNA binding region of NF-kappaB in complex with Ikappa Balpha. A model of the interactions in the complex is proposed based on our observations and the crystal structures of Rel/NF-kappaB dimers and the ankyrin domains of related proteins.

Publication types

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

MeSH terms

  • Base Sequence
  • DNA Primers
  • DNA-Binding Proteins / isolation & purification
  • DNA-Binding Proteins / metabolism*
  • Dimerization
  • Fluorescence Polarization Immunoassay
  • I-kappa B Proteins*
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism*
  • Nuclear Localization Signals*
  • Recombinant Proteins / metabolism

Substances

  • DNA Primers
  • DNA-Binding Proteins
  • I-kappa B Proteins
  • NF-kappa B
  • Nuclear Localization Signals
  • Recombinant Proteins
  • NF-KappaB Inhibitor alpha