Comparison of a retroviral protease in monomeric and dimeric states

Retroviral proteases RPs are of high interest owing to their crucial role in the maturation process of retroviral particles. RPs are obligatory homodimers, with a pepsin like active site built around two aspartates in DTG triads that activate a water molecule, as the nucleophile, under two flap loops. Mason Pfizer monkey virus M PMV is unique among retroviruses as its protease is also stable in the monomeric form, as confirmed by an existing crystal structure of a 13 amp; 8197;kDa variant of the protein M PMV PR and its previous biochemical characterization. In the present work, two mutants of M PMV PR, D26N and C7A D26N C106A, were crystallized in complex with a peptidomimetic inhibitor and one mutant D26N was crystallized without the inhibitor. The crystal structures were solved at resolutions of 1.6, 1.9 and 2.0 amp; 8197; , respectively. At variance with the previous study, all of the new structures have the canonical dimeric form of retroviral proteases. The protomers within a dimer differ mainly in the flap loop region, with the most extreme case observed in the apo structure, in which one flap loop is well defined while the other flap loop is not defined by electron density. The presence of the inhibitor molecules in the complex structures was assessed using polder maps, but some details of their conformations remain ambiguous. In all of the presented structures the active site contains a water molecule buried deeply between the Asn26 Thr27 Gly28 triads of the protomers. Such a water molecule is completely unique not only in retropepsins but also in aspartic proteases in general. The C7A and C106A mutations do not influence the conformation of the protein. The Cys106 residue is properly placed at the homodimer interface area for a disulfide cross link, but the reducing conditions of the crystallization experiment prevented S S bond formation. An animated Interactive 3D Complement I3DC is available in Proteopedia .

Crystal structures of inhibitor complexes of M‐PMV

Mason Pfizer monkey virus protease PR was crystallized in complex with two pepstatin based inhibitors in P1 space group. In both crystal structures, the extended flap loops that lock the inhibitor substrate over the active site, are visible in the electron density either completely or with only small gaps, providing the first observation of the conformation of the flap loops in dimeric complex form of this retropepsin. The H bond network in the active site with D26N mutation differs from that reported for the P21 crystal structures and is similar to a rarely occurring system in HIV 1 P

Crystal structures of inhibitor complexes of M PMV protease with visible flap loops

Mason Pfizer monkey virus protease PR was crystallized in complex with two pepstatin based inhibitors in P1 space group. In both crystal structures, the extended flap loops that lock the inhibitor substrate over the active site, are visible in the electron density either completely or with only small gaps, providing the first observation of the conformation of the flap loops in dimeric complex form of this retropepsin. The H bond network in the active site with D26N mutation differs from that reported for the P21 crystal structures and is similar to a rarely occurring system in HIV 1 P

The role of the S-S bridge in retroviral protease function and virion maturation

Retroviral proteases are translated as a part of Gag-related polyproteins, and are released and activated during particle release. Mason-Pfizer monkey virus (M-PMV) Gag polyproteins assemble into immature capsids within the cytoplasm of the host cells

Crystal structure of monomeric retroviral protease solved by protein folding game players

Following the failure of a wide range of attempts to solve the crystal structure of M-PMV retroviral protease by molecular replacement, we challenged players of the protein folding game Foldit to produce accurate models of the protein. Remarkably, Foldit players were able to generate models of sufficient quality for successful molecular replacement and subsequent structure determination. The refined structure provides new insights for the design of antiretroviral drugs