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M9490473.TXT
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Document 0473
DOCN M9490473
TI Nucleolar protein B23: bacterial expression, purification,
oligomerization and secondary structures of two isoforms.
DT 9411
AU Umekawa H; Chang JH; Correia JJ; Wang D; Wingfield PT; Olson MO;
Department of Biochemistry, University of Mississippi Medical; Center,
Jackson 39216-4505.
SO Cell Mol Biol Res. 1993;39(7):635-45. Unique Identifier : AIDSLINE
MED/94332167
AB Protein B23 is an abundant nucleolar phosphoprotein and putative
ribosome assembly factor. Two forms of the protein, B23.1 and B23.2,
contain 292 and 257 amino acids, respectively, and differ only in their
C-terminal sequences. The two B23 isoforms have been produced in
Escherichia coli using the pKK223-3 expression vector and purified to
near homogeneity. The purification utilized ammonium sulfate
fractionation followed by chromatography on DEAE-cellulose,
heparin-Sepharose and Bio-Rad Q. By combined gel filtration and
sedimentation analyses, both B23.1 and B23.2 formed multimers of Mr 210
to 255 kDa (apparent hexamers), suggesting that the differences in
C-terminal ends of of the isoforms do not affect oligomerization. The
oligomerization was not dependent on disulfide bond formation. The
circular dichroism spectra of recombinant proteins B23.1 and B23.2 were
similar suggesting that the carboxyl-terminal difference in the two
proteins does not markedly influence overall secondary structure. Using
routines for fitting the CD spectra to those of basis vectors the
recombinant B23 isoforms appeared to be composed predominantly of
beta-sheet and beta-turn secondary structures. Protein B23 from HeLa
cell nuclei was recently shown to have a high affinity for the HIV-1 Rev
protein. Using sucrose density gradient centrifugation it was shown that
both recombinant proteins B23.1 and B23.2, as well as B23.1 isolated
from Novikoff hepatoma nucleoli, were capable of binding the Rev
protein.
DE Cell Nucleus/METABOLISM Centrifugation, Density Gradient
Chromatography, Affinity Chromatography, DEAE-Cellulose
Chromatography, Gel Chromatography, Ion Exchange Circular Dichroism
Cloning, Molecular/METHODS Escherichia coli/*METABOLISM Gene Products,
rev/METABOLISM Hela Cells Human HIV-1/METABOLISM Macromolecular
Systems Nuclear Proteins/*BIOSYNTHESIS/*CHEMISTRY/ISOLATION & PURIF
Phosphoproteins/BIOSYNTHESIS/CHEMISTRY Plasmids *Protein Structure,
Secondary Recombinant Proteins/*BIOSYNTHESIS/CHEMISTRY/ISOLATION &
PURIF Restriction Mapping 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).