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Crystallographic Studies of Proteases Crystallographic studies of proteases have been an important area of research of this Section since its establishment. We have been particularly active in the investigation of structure-function relationship in aspartic proteases, including clinically important retroviral enzymes. Our studies of HIV protease, although no longer a major target of active research, are still ongoing and concentrate on the investigation of drug-resistant variants and their complexes with inhibitors. We have investigated structure-function relationship in retroviral proteases from several other sources such as FIV, RSV, and HTLV-1. Cockroach allergen Bla g 2 was shown to be an inactive aspartic protease and we solved its structure by itself, and in a complex with several specific antibodies. We have determined the structure of a unique histoaspartic protease, an enzyme with the pepsin fold, but a vastly different mechanism. We found that Shigella virulence factor VirA is a putative protease with a novel fold, and we are examining its structural and enzymatic properties. We have established an extensive program of investigating serine-carboxyl peptidases (sedolisins), a family that was first characterized based on crystal structures solved in this laboratory and that is found in many different organisms. We are also investigating the bacterial ATP-dependent protease Lon, finding that its proteolytic domain has a unique fold and thus establishes a new family of proteases with a Ser-Lys catalytic dyad. We have solved the structures of the proteolytic domain of A and B type Lon proteases, encoded by E. coli and Archaeoglobus fulgidus, as well as the N-terminal and α domains of E. coli Lon. Lectins with Antiviral Activity We have been involved in studies of several lectins with antiviral activities, some of them used in pre-clinical trials as potential drugs preventing HIV infection. We have solved the structure of griffithsin, as free protein and complexed with a number of mono- and disaccharides, explaining the structural basis for its tight binding to branched mannose-rich carbohydrates. We have also solved the structure of another lectin, scytovirin, and are investigating its mode of carbohydrate binding. Proteins Involved in Ribosome Biogenesis and Tumor Suppression Two related serine protein kinases, Rio1 and Rio2, are involved in processing 20S pre-RNA to 18S ribosomal RNA. Their crystal structures, solved by our Section, established that they belong to a novel family of kinases with a truncated substrate-binding region, although they are capable of both self- and trans-phosphorylation. We have established the sites of autophosphorylation for both of them. We are currently investigating their catalytic properties and potential biological roles. We have also solved the structure of the C-terminal MA3 domain of Pdcd4, explaining how that tumor suppressor factor inhibits translation initiation. Cytokines and Cytokine Receptors Our Section has been investigating the crystal structures of several cytokines and has made progress in preparing their receptor complexes. We have purified and crystallized complexes of IL-10 with its specific receptor and are studying complexes of several other cytokines related to IL-10, such as IL-19, IL-20, IL-22, IFN-λ1 and IFN-λ2. Our extramural collaborators include Anna Marie Skalka, Ph.D., Fox Chase Cancer Center; Ben Dunn, Ph.D., University of Florida; John Elder, Ph.D., The Scripps Research Institute; Kohei Oda, Ph.D., Kyoto Institute of Technology, Kyoto, Japan; Toru Nakayama, Ph.D., Tohoku University, Sendai, Japan; Rickey Yada, Ph.D., University of Guelph, Guelph, Canada; Mariusz Jaskolski, D.Sc., Adam Mickiewicz University, Poznan, Poland; and Tatyana Rotanova, D.Sc., Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia. |
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