title: Active-site residues of cyclophilin A are crucial for its incorporation into human immunodeficiency virus type 1 virions.
abstract: Human immunodeficiency virus type 1 (HIV-1) incorporates the cellular peptidyl-prolyl cis-trans isomerase cyclophilin A (CyPA), the cytosolic receptor for the immunosuppressant cyclosporin A (CsA). CsA inhibits the incorporation of CyPA and reduces HIV-1 virion infectivity but is inactive against closely related primate lentiviruses that do not interact with CyPA. The incorporation of CyPA into HIV-1 virions is mediated by a specific interaction with a proline-containing, solvent-exposed loop in the capsid (CA) domain of the Gag polyprotein. CsA, which disrupts the interaction with CA, binds at the active site of CyPA. To test whether active-site residues are also involved in the interaction with HIV-1 CA, we used a panel of previously characterized active-site mutants of human CyPA. Expression vectors for epitope-tagged wild-type and mutant CyPA were transfected into COS-gamma cells along with HIV-1 proviral DNA, and the virions produced were analyzed for the presence of tagged proteins. Cotransfection of the wild-type expression vector led to the incorporation of readily detectable amounts of epitope-tagged CyPA into HIV-1 virions. One CyPA mutant with a substantially decreased sensitivity to CsA was incorporated with wild-type efficiency, demonstrating that the requirements for binding to CsA and to HIV-1 CA are not identical. The remaining six CyPA mutants were incorporated with markedly reduced efficiency, providing in vivo evidence that HIV-1 CA interacts with the active site of CyPA.
authors.affiliation: Division of Human Retrovirology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA.
authors.forename: T
authors.initials: T
authors.lastname: Dorfman
authors.forename: A
authors.initials: A
authors.lastname: Weimann
authors.forename: A
authors.initials: A
authors.lastname: Borsetti
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
authors.forename: H G
authors.initials: HG
authors.lastname: Göttlinger
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D015394:Molecular Structure; D009154:Mutation; D019696:Peptidylprolyl Isomerase; D014771:Virion / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase