       Document 0224
 DOCN  M95A0224
 TI    Interaction of nucleolar protein B23 with peptides related to nuclear
       localization signals.
 DT    9510
 AU    Szebeni A; Herrera JE; Olson MO; Department of Biochemistry, University
       of Mississippi Medical; Center, Jackson 39216-4505, USA.
 SO    Biochemistry. 1995 Jun 27;34(25):8037-42. Unique Identifier : AIDSLINE
       MED/95315192
 AB    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)
 DE    Amino Acid Sequence  Antigens, Polyomavirus
       Transforming/CHEMISTRY/METABOLISM  Binding Sites  Binding, Competitive
       Dialysis  Ethylmaleimide  Gene Products, rev/CHEMISTRY/METABOLISM
       HIV-1/CHEMISTRY  Molecular Sequence Data  Nuclear
       Proteins/CHEMISTRY/*METABOLISM  Phosphorylation
       Protein-Serine-Threonine Kinases/METABOLISM  Support, U.S. Gov't, P.H.S.
       JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

