title: High-resolution structure of a retroviral protease folded as a monomer.
abstract: Mason-Pfizer monkey virus (M-PMV), a D-type retrovirus assembling in the cytoplasm, causes simian acquired immunodeficiency syndrome (SAIDS) in rhesus monkeys. Its pepsin-like aspartic protease (retropepsin) is an integral part of the expressed retroviral polyproteins. As in all retroviral life cycles, release and dimerization of the protease (PR) is strictly required for polyprotein processing and virion maturation. Biophysical and NMR studies have indicated that in the absence of substrates or inhibitors M-PMV PR should fold into a stable monomer, but the crystal structure of this protein could not be solved by molecular replacement despite countless attempts. Ultimately, a solution was obtained in mr-rosetta using a model constructed by players of the online protein-folding game Foldit. The structure indeed shows a monomeric protein, with the N- and C-termini completely disordered. On the other hand, the flap loop, which normally gates access to the active site of homodimeric retropepsins, is clearly traceable in the electron density. The flap has an unusual curled shape and a different orientation from both the open and closed states known from dimeric retropepsins. The overall fold of the protein follows the retropepsin canon, but the C(α) deviations are large and the active-site 'DTG' loop (here NTG) deviates up to 2.7 Å from the standard conformation. This structure of a monomeric retropepsin determined at high resolution (1.6 Å) provides important extra information for the design of dimerization inhibitors that might be developed as drugs for the treatment of retroviral infections, including AIDS.
authors.affiliation: Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, 60-780 Poznan, Poland.
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Gilski
authors.forename: Maciej
authors.initials: M
authors.lastname: Kazmierczyk
authors.forename: Szymon
authors.initials: S
authors.lastname: Krzywda
authors.forename: Helena
authors.initials: H
authors.lastname: Zábranská
authors.forename: Seth
authors.initials: S
authors.lastname: Cooper
authors.forename: Zoran
authors.initials: Z
authors.lastname: Popović
authors.forename: Firas
authors.initials: F
authors.lastname: Khatib
authors.forename: Frank
authors.initials: F
authors.lastname: DiMaio
authors.forename: James
authors.initials: J
authors.lastname: Thompson
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.forename: Iva
authors.initials: I
authors.lastname: Pichová
authors.forename: Mariusz
authors.initials: M
authors.lastname: Jaskolski
mesh_terms: D000818:Animals; D044966:Anti-Retroviral Agents / Q000627:therapeutic use; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004195:Disease Models, Animal; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology*; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity; D006801:Humans; D008251:Macaca; D016093:Mason-Pfizer monkey virus / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity; D058990:Molecular Targeted Therapy; D009154:Mutation / Q000235:genetics; D011487:Protein Conformation; D017510:Protein Folding; D016097:Simian Acquired Immunodeficiency Syndrome / Q000188:drug therapy / Q000821:virology*
chemical_list: D044966:Anti-Retroviral Agents; D010450:Endopeptidases; C445563:Mason-Pfizer monkey virus protease
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