The intriguing cyclophilin A-HIV-1 Vpr interaction: prolyl cis/trans isomerisation catalysis and specific binding

• Published in: BMC structural biology 2010-10, Vol.10 (1), p.31-31, Article 31
• Main Authors: Solbak, Sara M, Reksten, Tove R, Wray, Victor, Bruns, Karsten, Horvli, Ole, Raae, Arnt J, Henklein, Petra, Henklein, Peter, Röder, Rene, Mitzner, David, Schubert, Ulrich, Fossen, Torgils
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical properties; Cyclophilin A - metabolism; Enzymes; Health aspects; HIV (Viruses); Human immunodeficiency virus 1; Humans; Isomerization; Kinetics; Nuclear Magnetic Resonance, Biomolecular; Peptidylprolyl Isomerase - metabolism; Physiological aspects; Proline - metabolism; Protein Binding; Software; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Spectrum analysis; Studies; Surface Plasmon Resonance; Viral proteins; Virus Replication - physiology; vpr Gene Products, Human Immunodeficiency Virus - metabolism
• ISSN: 1472-6807; 1472-6807
• DOI: 10.1186/1472-6807-10-31

Cyclophilin A (CypA) represents a potential target for antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication, although the mechanism through which CypA modulates HIV-1 infectivity still remains unclear. The interaction of HIV-1 viral protein R (Vpr) with the human peptidyl prolyl isomerase CypA is known to occur in vitro and in vivo. However, the nature of the interaction of CypA with Pro-35 of N-terminal Vpr has remained undefined. Characterization of the interactions of human CypA with N-terminal peptides of HIV-1 Vpr has been achieved using a combination of nuclear magnetic resonace (NMR) exchange spectroscopy and surface plasmon resonance spectroscopy (SPR). NMR data at atomic resolution indicate prolyl cis/trans isomerisation of the highly conserved proline residues Pro-5, -10, -14 and -35 of Vpr are catalyzed by human CypA and require only very low concentrations of the isomerase relative to that of the peptide substrates. Of the N-terminal peptides of Vpr only those containing Pro-35 bind to CypA in a biosensor assay. SPR studies of specific N-terminal peptides with decreasing numbers of residues revealed that a seven-residue motif centred at Pro-35 consisting of RHFPRIW, which under membrane-like solution conditions comprises the loop region connecting helix 1 and 2 of Vpr and the two terminal residues of helix 1, is sufficient to maintain strong specific binding. Only N-terminal peptides of Vpr containing Pro-35, which appears to be vital for manifold functions of Vpr, bind to CypA in a biosensor assay. This indicates that Pro-35 is essential for a specific CypA-Vpr binding interaction, in contrast to the general prolyl cis/trans isomerisation observed for all proline residues of Vpr, which only involve transient enzyme-substrate interactions. Previously suggested models depicting CypA as a chaperone that plays a role in HIV-1 virulence are now supported by our data. In detail the SPR data of this interaction were compatible with a two-state binding interaction model that involves a conformational change during binding. This is in accord with the structural changes observed by NMR suggesting CypA catalyzes the prolyl cis/trans interconversion during binding to the RHFP35RIW motif of N-terminal Vpr.