Document 0744
 DOCN  M9550744
 TI    Fusogenic activity of amino-terminal region of HIV type 1 Nef protein.
 DT    9505
 AU    Curtain CC; Separovic F; Rivett D; Kirkpatrick A; Waring AJ; Gordon LM;
       Azad AA; Biomolecular Research Institute, Parkville, Victoria,
       Australia.
 SO    AIDS Res Hum Retroviruses. 1994 Oct;10(10):1231-40. Unique Identifier :
       AIDSLINE MED/95151360
 AB    We have studied two isoforms of Nef, Nef-27 and Nef-25, which were
       produced in E. coli. Nef-25 lacked the first 18 N-terminal residues of
       Nef-27 and both were nonmyristylated. Nef-27 fuses small unilamellar
       dipalmitoyl phosphatidylcholine vesicles (SUVs), as indicated by
       enhanced light scattering of SUVs and lipid mixing using
       concentration-dependent fluorescence dequenching. Nef-27 also causes the
       appearance of a shifted isotropic peak in the 31P NMR spectra of these
       vesicles, suggesting that protein interactions induce nonlamellar lipid
       structures. Recombinant Nef-25, which lacks only the 18 N-terminal
       residues of Nef-27, does not fuse vesicles and has little effect on the
       31P NMR spectra. On the other hand, synthetic peptides consisting of 18
       or 21 of the N-terminal residues of Nef-27 are strongly membrane
       perturbing, causing vesicle fusion and inducing isotropic peaks in the
       31P NMR spectrum. Endogenous fluorescence spectra of the N-terminal
       peptide (21 residues) with SUVs show that the N-terminal sequence of Nef
       may achieve these perturbing effects by inserting its hydrophobic side
       into the lipid bilayer. Theoretical calculations using hydrophobic
       moment plot analysis indicate that short-length stretches (i.e., six
       amino acid residues) of the N-terminal sequence may insert into the
       lipid bilayer as multimeric alpha helices or beta sheets. The
       above-described membrane activities of Nef-27, which principally reside
       in its N-terminal domain, may play critical role(s) in certain
       functional properties of the full-length protein. For example, the
       fusogenic activity of the N-terminal sequence may be involved in the
       extracellular release of Nef-27, much of which appears to be associated
       with small membrane vesicles. The fusion activity may also be relevant
       to the ability of Nef-27 to downregulate CD4 and IL-2 receptors when
       this protein is electroporated into cultured lymphocytes, an activity
       not possessed by Nef-25.
 DE    Amino Acid Sequence  Antigens, Bacterial/CHEMISTRY  Comparative Study
       Gene Products, nef/BIOSYNTHESIS/CHEMISTRY/*METABOLISM  HIV-1/*METABOLISM
       Light  *Liposomes  *Membrane Fusion  Molecular Sequence Data  Nuclear
       Magnetic Resonance  Peptide Fragments/*CHEMISTRY/CHEMICAL SYNTHESIS
       Protein Structure, Secondary  Recombinant
       Proteins/BIOSYNTHESIS/*METABOLISM  Scattering, Radiation  Sequence
       Homology, Amino Acid  Spectrometry, Fluorescence  Support, Non-U.S.
       Gov't  Support, U.S. Gov't, P.H.S.  *1,2-Dipalmitoylphosphatidylcholine
       JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
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