title: Solution structure of the human immunodeficiency virus type 1 p6 protein.
abstract: The human immunodeficiency virus type 1 p6 protein represents a docking site for several cellular and viral binding factors and fulfills major roles in the formation of infectious viruses. To date, however, the structure of this 52-amino acid protein, by far the smallest lentiviral protein known, either in its mature form as free p6 or as the C-terminal part of the Pr55 Gag polyprotein has not been unraveled. We have explored the high resolution structure and folding of p6 by CD and NMR spectroscopy. Under membranous solution conditions, p6 can adopt a helix-flexible helix structure; a short helix-1 (amino acids 14-18) is connected to a pronounced helix-2 (amino acids 33-44) by a flexible hinge region. Thus, p6 can be subdivided into two distinct structural and functional domains; helix-2 perfectly defines the region that binds to the virus budding factor AIP-1/ALIX, indicating that this structure is required for interaction with the endosomal sorting complex required for transport. The PTAP motif at the N terminus, comprising the primary late assembly domain, which is crucial for interaction with another cellular budding factor, Tsg101, does not exhibit secondary structure. However, the adjacent helix-1 may play an indirect role in the specific complex formation between p6 and the binding groove in Tsg101. Moreover, binding studies by NMR demonstrate that helix-2, which also comprises the LXXLF motif required for incorporation of the human immunodeficiency virus type 1 accessory protein Vpr into budding virions, specifically interacts with the Vpr binding region, indicating that under the specific solution conditions used for structure analysis, p6 adopted a functional conformation.
authors.affiliation: Department of Structural Biology, Gesellschaft für Biotechnologische Forschung, D-38124 Braunschweig, Germany.
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
authors.forename: Victor
authors.initials: V
authors.lastname: Wray
authors.forename: Karsten
authors.initials: K
authors.lastname: Bruns
authors.forename: Judhi
authors.initials: J
authors.lastname: Rachmat
authors.forename: Peter
authors.initials: P
authors.lastname: Henklein
authors.forename: Uwe
authors.initials: U
authors.lastname: Tessmer
authors.forename: Annette
authors.initials: A
authors.lastname: Maczurek
authors.forename: Patricia
authors.initials: P
authors.lastname: Klinger
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schubert
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D056827:Endosomal Sorting Complexes Required for Transport; D015683:Gene Products, gag / Q000737:chemistry* / Q000378:metabolism; D016336:Gene Products, vpr / Q000737:chemistry; D006801:Humans; D047468:Immunoprecipitation; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011522:Protons; D014157:Transcription Factors / Q000737:chemistry; D054301:gag Gene Products, Human Immunodeficiency Virus; D000099177:Tsg101 Protein
chemical_list: D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D015683:Gene Products, gag; D016336:Gene Products, vpr; D010455:Peptides; D011522:Protons; D014157:Transcription Factors; D054301:gag Gene Products, Human Immunodeficiency Virus; D000099177:Tsg101 Protein; C083002:p6 gag protein, Human immunodeficiency virus 1