title: The host-pathogen interaction of human cyclophilin A and HIV-1 Vpr requires specific N-terminal and novel C-terminal domains.
abstract: BACKGROUND
  Cyclophilin A (CypA) represents a potential key molecule in future antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication. CypA interacts with the virus proteins Capsid (CA) and Vpr, however, the mechanism through which CypA influences HIV-1 infectivity still remains unclear.
  
  
  RESULTS
  Here the interaction of full-length HIV-1 Vpr with the host cellular factor CypA has been characterized and quantified by surface plasmon resonance spectroscopy. A C-terminal region of Vpr, comprising the 16 residues 75GCRHSRIGVTRQRRAR90, with high binding affinity for CypA has been identified. This region of Vpr does not contain any proline residues but binds much more strongly to CypA than the previously characterized N-terminal binding domain of Vpr, and is thus the first protein binding domain to CypA described involving no proline residues. The fact that the mutant peptide Vpr75-90 R80A binds more weakly to CypA than the wild-type peptide confirms that Arg-80 is a key residue in the C-terminal binding domain. The N- and C-terminal binding regions of full-length Vpr bind cooperatively to CypA and have allowed a model of the complex to be created. The dissociation constant of full-length Vpr to CypA was determined to be approximately 320 nM, indicating that the binding may be stronger than that of the well characterized interaction of HIV-1 CA with CypA.
  
  
  CONCLUSIONS
  For the first time the interaction of full-length Vpr and CypA has been characterized and quantified. A non-proline-containing 16-residue region of C-terminal Vpr which binds specifically to CypA with similar high affinity as full-length Vpr has been identified. The fact that this is the first non-proline containing binding motif of any protein found to bind to CypA, changes the view on how CypA is able to interact with other proteins. It is interesting to note that several previously reported key functions of HIV-1 Vpr are associated with the identified N- and C-terminal binding domains of the protein to CypA.
authors.affiliation: Centre of Pharmacy, University of Bergen, N-5007 Bergen Norway.
authors.forename: Sara M Ø
authors.initials: SM
authors.lastname: Solbak
authors.forename: Victor
authors.initials: V
authors.lastname: Wray
authors.forename: Ole
authors.initials: O
authors.lastname: Horvli
authors.forename: Arnt J
authors.initials: AJ
authors.lastname: Raae
authors.forename: Marte I
authors.initials: MI
authors.lastname: Flydal
authors.forename: Petra
authors.initials: P
authors.lastname: Henklein
authors.forename: Peter
authors.initials: P
authors.lastname: Henklein
authors.forename: Manfred
authors.initials: M
authors.lastname: Nimtz
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schubert
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D021984:Cyclophilin A / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D054325:vpr Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D054325:vpr Gene Products, Human Immunodeficiency Virus; C514912:vpr protein, Human immunodeficiency virus 1; D021984:Cyclophilin A