Document 0342
 DOCN  M9550342
 TI    Dimerization kinetics of HIV-1 and HIV-2 reverse transcriptase: a two
       step process.
 DT    9505
 AU    Divita G; Rittinger K; Geourjon C; Deleage G; Goody RS;
       Max-Planck-Institut fur Medizinische Forschung, Abteilung; Biophysik,
       Heidelberg, Germany.
 SO    J Mol Biol. 1995 Feb 3;245(5):508-21. Unique Identifier : AIDSLINE
       MED/95147274
 AB    The dimerization processes of the human immunodeficiency virus (HIV)
       types 1 and 2 reverse transcriptase (RTs) from their subunits have been
       investigated using a number of complementary approaches (fluorescence
       spectroscopy, size exclusion-HPLC and polymerase activity assay). The
       formation of the native heterodimeric form of HIV-1 and HIV-2 RT occurs
       in a two step process. The first step is a concentration-dependent
       association of the two subunits (p66 and p51) to give a heterodimeric
       intermediate, which slowly isomerizes to the mature heterodimeric form
       of the enzyme. For both RTs, the first step behaves as a second order
       reaction with similar association rate constants (in the range of 2 x
       10(4) to 4 x 10(4) M-1 s-1). This initial dimerization results in a 25%
       quenching of the intrinsic fluorescence and a 30% decrease in the
       accessibility of the tryptophan hydrophobic cluster to solvent as
       revealed by iodide quenching experiments and by monitoring the binding
       of 1-anilino-8-naphthalenesulphonate. The formation of the
       intermediate-RT form appears to involve hydrophobic regions of the
       subunits containing tryptophan residues. This intermediate form is
       devoid of polymerase activity, but is able to bind primer/template with
       high affinity. The final stage of the mature RT-heterodimer formation
       occurs in a slow first order reaction, which is 12-fold faster for HIV-2
       (1.2 h-1) than HIV-1 RT (0.1 h-1). At micromolar concentrations, this
       slow isomerization constitutes the rate limiting step of the RT
       maturation and the structural change involved appears to be partly
       associated with the catalytic site, as shown using fluorescent labelled
       primer/template. On the basis of both the presently available X-ray
       structure of the HIV-1 RT and the predicted structure of HIV-2 RT, the
       thumb subdomain of the p51 subunit seems to be involved in this
       maturation step, which is probably the interaction of this domain with
       the RNAse H domain of the large subunit. The placement of the fingers
       subdomain of p51 in the palm subdomain of the p66 subunit may also be
       associated with formation of mature heterodimeric RTs.
 DE    Anilino Naphthalenesulfonates  Base Sequence  Binding Sites  Biopolymers
       Chromatography, Gel  Chromatography, High Pressure Liquid  DNA Primers
       HIV-1/*ENZYMOLOGY  HIV-2/*ENZYMOLOGY  Kinetics  Molecular Sequence Data
       Protein Structure, Secondary  Reverse Transcriptase/*METABOLISM
       Spectrometry, Fluorescence  Support, Non-U.S. Gov't  JOURNAL ARTICLE

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