Interaction of nucleolar protein B23 with peptides related to nuclear localization signals

Biochemistry. 1995 Jun 27;34(25):8037-42. doi: 10.1021/bi00025a009.


Nucleolar protein B23 is a putative ribosome assembly factor with a high affinity for peptides containing nuclear localization signals (NLSs). The interactions of various NLS-containing peptides with two B23 isoforms (B23.1 and B23.2) were examined using equilibrium dialysis and Scatchard analyses. The KD for protein B23 binding to a peptide containing the SV40 T-antigen NLS sequence was approximately 1 microM with a stoichiometry of 1:1 (peptide:protein). No significant differences were seen between the two B23 isoforms in their affinities for any of the peptides tested. Binding by a reverse sequence SV40 T-NLS peptide showed a nonlinear Scatchard plot: this peptide was unable displace the correct sequence peptide, suggesting that the reverse sequence peptide binds to a different site on the protein. A peptide containing the sequence required for nucleolar localization of the HIV-1 Rev protein had an affinity for B23 approximately 10-fold greater than that of the SV40 T-NLS. However, with a sequence sufficient only for Rev location in the nucleoplasm, the affinity for B23 was diminished to a level between that of the longer Rev sequence and the SV40 T-NLS. In competition binding assays, the Rev NLS peptide was able to displace the SV40 T NLS, indicating that both peptides bind to the same site on protein B23. There was no detectable binding to protein B23 by a peptide containing the bipartite NLS of nucleoplasmin. Phosphorylation of protein B23 by casein kinase II enhanced its affinity for the SV40 T- and Rev-derived peptides approximately 2-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Antigens, Polyomavirus Transforming / chemistry
  • Antigens, Polyomavirus Transforming / metabolism
  • Binding Sites
  • Binding, Competitive
  • Casein Kinase II
  • Dialysis
  • Ethylmaleimide
  • Gene Products, rev / chemistry
  • Gene Products, rev / metabolism
  • HIV-1 / chemistry
  • Molecular Sequence Data
  • Nuclear Localization Signals
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism*
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism
  • rev Gene Products, Human Immunodeficiency Virus


  • Antigens, Polyomavirus Transforming
  • Gene Products, rev
  • Nuclear Localization Signals
  • Nuclear Proteins
  • rev Gene Products, Human Immunodeficiency Virus
  • nucleophosmin
  • Casein Kinase II
  • Protein-Serine-Threonine Kinases
  • Ethylmaleimide