Document 0899
 DOCN  M95A0899
 TI    Conformation and stability of recombinant HIV-1 capsid protein p24
       (rp24).
 DT    9510
 AU    Misselwitz R; Hausdorf G; Welfle K; Hohne WE; Welfle H; Institute of
       Biochemistry, Medical Faculty (Charite), Humboldt; University, Berlin,
       Germany.
 SO    Biochim Biophys Acta. 1995 Jul 3;1250(1):9-18. Unique Identifier :
       AIDSLINE MED/95337139
 AB    Conformation and stability of the recombinant protein HIV-1 rp24 were
       analyzed by circular dichroism, fluorescence spectroscopy and
       differential scanning calorimetry under different solvent conditions.
       From circular dichroism measurements, HIV-1 rp24 at pH 5.8 can be
       classified as an all alpha-helical protein. A fluorescence maximum of
       about 330 nm indicates a predominantly hydrophobic environment of the
       five tryptophan residues. The GdnHCl-induced unfolding curves monitored
       by CD and fluorescence are sigmoidal and single phasic and the midpoints
       of transitions are independent on the protein concentration. For the
       calculation of free energy of unfolding delta GuH2O a 'two-state' model
       was applied. The calculated values are between 18 and 24 kJ/mol and thus
       on the lower limit of the conformational stability of globular proteins.
       Melting experiments at pH 5.8 are impaired by a strong irreversible
       aggregation at higher temperatures. However, at pH 3.0 and in the
       presence of 0.1% (w/v) ocytl beta-glucopyranoside the melting curves
       show a large degree of reversibility with a Tm value of 38 degrees C and
       a molar enthalpy change delta Hm of 218 kJ/mol. At pH < 2.5 HIV-1 rp24
       can adopt a new conformation which is characterized by a high
       alpha-helical content, a strongly decreased CD in the aromatic region, a
       red-shift of the fluorescence spectrum and a strong binding of ANS.
       These spectral features of the acid-induced conformational state are
       similar to those obtained for molten globule-like folding states. HIV-1
       rp24 unfolds cooperatively at pH 2.0 in the concentration range of about
       1.5-3.0 M GdnHCl. The calculated values delta GuH2O at pH 2.0 of about
       12 kJ/mol are significantly decreased in comparison to the delta GuH2O
       values of the protein at pH 5.8.
 DE    Anilino Naphthalenesulfonates/CHEMISTRY  Calorimetry, Differential
       Scanning  Capsid/*CHEMISTRY  Circular Dichroism  Gene Products,
       gag/*CHEMISTRY  Hydrogen-Ion Concentration  HIV-1/*CHEMISTRY  *Protein
       Conformation  Protein Folding  Recombinant Proteins/CHEMISTRY
       Spectrometry, Fluorescence  JOURNAL ARTICLE

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