CRYSTAL STRUCTURE OF THE COMPLEX OF PKR AND HIV TAR RNA

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our work is in three parts: a) Crystallographic study of complex of PKR and HIV TAR RNA. b) Crystallographic study of HIV TAR structure at high resolution c) Crystallographic study of IKK kinase complex. The human dsRNA activated protein kinase (PKR) is a product of an interferon-induced gene and a key component of the human innate defense system. In response to viral infection, PKR inhibits translation factor eIF-2a via phosphorylation of its serine 51 residue. PKR is involved in transcription by regulating some important transcription factors. A critical step in the activation of PKR is the interaction of dsRNA in a sequenceindependent manner. Upon binding, PKR undergoes conformational rearrangement and autophosphorylation. The long-term objective of this study is to understand the molecular nature of the dsRNA:PKR interaction and protein kinase activation. HIV-1 TAR dsRNA activates PKR both in vivo and in vitro, exhibiting a concentration-dependent, activation-inhibition curve typical of dsRNA To obtain insight into the molecular nature of dsRNA:PKR interaction, the complex of PKR and TAR 57 RNA was crystallized in a C2 space group with cell parameters: 80.42, 45.99, 254.42 ¿ and a=90?00, b=97?.25 and g=90?.00. The preliminary results indicate the presence of four PKR molecules in the unit cell and the possibility of a composition of two PKR molecules and one TAR 1 57 RNA. The results are consistent with those of the Neutron Scattering studies.