Self-assembling dendrimers for biomedical applications / 中国药科大学学报

@#Dendrimers, a special class of synthetic polymers known for their well-defined ramified structures and unique multivalent cooperativity, hold great promise for various biomedical applications. However, preparation of defect-free dendrimers of high-generation on a large scale remains challenging because of the tedious and time-consuming synthesis as well as difficult purification. To overcome these limitations, an alternative strategy based on self-assembling approach has been developed to construct supramolecular dendrimers using small amphiphilic dendrimer-building units. By virtue of the amphiphilic nature, these small dendrimer-building units self-assemble and form large non-covalent supramolecular dendritic structures that mimic high-generation covalent dendrimers. Here, we present a brief overview of the supramolecular dendrimers developed in our group for the delivery of nucleic acid therapeutics, anticancer drug and imaging agents.

Three-dimensional domain swapping as a mechanism to lock the active conformation in a super-active octamer of SARS-CoV main protease

Proteolytic processing of viral polyproteins is indispensible for the lifecycle of coronaviruses. The main protease (M(pro)) of SARS-CoV is an attractive target for anti-SARS drug development as it is essential for the polyprotein processing. M(pro) is initially produced as part of viral polyproteins and it is matured by autocleavage. Here, we report that, with the addition of an N-terminal extension peptide, M(pro) can form a domain-swapped dimer. After complete removal of the extension peptide from the dimer, the mature M(pro) self-assembles into a novel super-active octamer (AO-M(pro)). The crystal structure of AO-M(pro) adopts a novel fold with four domain-swapped dimers packing into four active units with nearly identical conformation to that of the previously reported M(pro) active dimer, and 3D domain swapping serves as a mechanism to lock the active conformation due to entanglement of polypeptide chains. Compared with the previously well characterized form of M(pro), in equilibrium between inactive monomer and active dimer, the stable AO-M(pro) exhibits much higher proteolytic activity at low concentration. As all eight active sites are bound with inhibitors, the polyvalent nature of the interaction between AO-M(pro) and its polyprotein substrates with multiple cleavage sites, would make AO-M(pro) functionally much more superior than the M(pro) active dimer for polyprotein processing. Thus, during the initial period of SARS-CoV infection, this novel active form AOM(pro) should play a major role in cleaving polyproteins as the protein level is extremely low. The discovery of AOM(pro) provides new insights about the functional mechanism of M(pro) and its maturation process.