4. Study on the Structure of Dengue Virus NS2B–NS3p in Complex with Aprotinin

Dengue virus, a member of Flaviviridae, is one of the most prevalent Mosquito-borne viruses in tropical and subtropical regions of the world. It causes a range of clinical diseases, such as dengue fever, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) [1]. Lack of approved vaccine or effective antiviral therapy for these diseases puts millions of lives at risk. Like other flaviviruses, the genome of dengue virus contains a positive single-stranded 11-kilobases RNA, which encodes three structural proteins (capsid protein C, membrane protein M, and envelope protein E) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) [2]. The N-terminus of NS3 (NS3p) functions as a serine protease, whose catalytic activity requires NS2B. A combination of NS2B–NS3p and the host proteases, cleaves the viral polyprotein into individual mature proteins. Therefore it is essential for viral replication [3]. Aprotinin, a classic inhibitor for trypsin and related proteolytic enzymes, was reported to inhibit the activity of NS2B–NS3p protease at submicromolar concentration [4]. In this chapter, the backbone 1H, ¹⁵N, ¹³C resonance assignments of the N terminal fragment of NS2B (4.8 kDa) and NS3p (18.5 kDa) in complex with aprotinin (6.5 kDa) is reported, which provides a requisite step for determining the solution structure of the complex. It is also important for screening and developing new antiviral drugs by structure-based designing strategies.