Directional self-assembly of uncharged molecules in water is am ajor challenge in supramolecular chemistry. Herein,i ti sdemonstrated that peptide-based cavitands wrap around ah ydrophobic core (fullerene C 60 )b yacombination of the hydrophobic effect and hydrogen-bonding interactions to form highly ordered three-componentc omplexes in water that resemblet he molten-globule stage of proteinf olding. The complexesw ere characterized by DOSY NMR spectroscopy,s mall-angleX -ray scattering, andc ircular dichroism, and their structuresw ere confirmed by X-ray crystallography.E nhancemento ft he CD signalsb yn early one order of magnitude and increased hydrolytic stability of hydrazone bonds of the complexes relative to the nonassembled species were observed.I nc ontrast, DMSO and DMSO/ waterm ixtures were found to be highly disintegrative for these complexes. Interestingly,s ome cavitands cano nly be synthesized in the presence of the hydrophobic template followed by disassemblyoft he complexes.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
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 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 Å , 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 at http://proteopedia.org/w/Journal:Acta_Cryst_D:S2059798319011355.
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 P2 1 crystal structures and is similar to a rarely occurring system in HIV-1 PR.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.