       Document 0983
 DOCN  M9620983
 TI    A trimeric subdomain of the simian immunodeficiency virus envelope
       glycoprotein.
 DT    9602
 AU    Blacklow SC; Lu M; Kim PS; Howard Hughes Medical Institute, Whitehead
       Institute for; Biomedical Research, Department of Biology,
       Massachusetts; Institute of Technology, Cambridge 02142, USA.
 SO    Biochemistry. 1995 Nov 21;34(46):14955-62. Unique Identifier : AIDSLINE
       MED/96072732
 AB    Previous attempts to define the oligomeric state of the HIV and SIV
       envelope glycoproteins have yielded conflicting results. We have
       produced in Escherichia coli a recombinant model for the ectodomain of
       the SIV envelope protein gp41 and have identified a small, trimeric
       subdomain by proteolytic digestion of this gp41 fragment. The subdomain
       assembles from two peptide fragments, spanning residues 28-80 (N28-80)
       and residues 107-149 (C107-149) of SIV gp41. Each of these peptides
       contains a 4,3-hydrophobic repeat, the hallmark of coiled-coil
       sequences. Upon mixing, the peptides form a highly helical, trimeric
       complex [3(N+C)] that resists proteolysis and has a melting temperature
       (Tm) above 90 degrees C in physiological buffer. The N- and C-terminal
       fragments are antiparallel to each other in the complex, as judged by
       the observation that digestion of a variant recombinant protein
       truncated at the amino terminus yields a C-terminal fragment shortened
       at its carboxy terminus. The N28-80 peptide contains more positions
       within the heptad repeat than C107-149 that are predominantly
       hydrophobic, suggesting that N28-80 is buried in the interior of the
       complex. We propose that the complex consists of a parallel, trimeric
       coiled-coil of the N-terminal peptide, encircled by three C-terminal
       peptide helices arranged in an antiparallel fashion, and that this
       complex forms a core within the gp41 extracellular domain.
 DE    Amino Acid Sequence  Chromatography, High Pressure Liquid  Circular
       Dichroism  Comparative Study  Heat  Hydrogen-Ion Concentration
       HIV/CHEMISTRY  Macromolecular Systems  Membrane Glycoproteins/*CHEMISTRY
       Molecular Sequence Data  Peptide Fragments/CHEMISTRY/METABOLISM  Protein
       Folding  Protein Structure, Secondary  Recombinant Proteins/CHEMISTRY
       Retroviridae Proteins/*CHEMISTRY  Serine Proteinases/METABOLISM
       Support, Non-U.S. Gov't  SIV/*CHEMISTRY  Viral Envelope
       Proteins/*CHEMISTRY  JOURNAL ARTICLE

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

