title: A trimeric subdomain of the simian immunodeficiency virus envelope glycoprotein.
abstract: 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.
authors.affiliation: Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Biology, Massachusetts Institute of Technology, Cambridge 02142, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Blacklow
authors.forename: M
authors.initials: M
authors.lastname: Lu
authors.forename: P S
authors.initials: PS
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D019286:Endopeptidase K; D006678:HIV / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D012191:Retroviridae Proteins / Q000737:chemistry*; D012697:Serine Endopeptidases / Q000378:metabolism; D015302:Simian Immunodeficiency Virus / Q000737:chemistry*; D014759:Viral Envelope Proteins / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012191:Retroviridae Proteins; C082614:SIV envelope protein gp41; D014759:Viral Envelope Proteins; D012697:Serine Endopeptidases; D019286:Endopeptidase K