| Structural and functional studies of retroviral nucleocapsid proteins. | |
Abstract/OtherAbstract
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The nucleocapsid protein (NC) is an essential, so-called "structural," retroviral protein. NC participation is implicated in numerous retroviral processes, including selection, specific dimerization, and histone-like packaging of retroviral genomic RNA; primer RNA annealing; reverse transcription and integration; and virion maturation. This research expands the structural and functional data for two retroviral NCs, aiding in rationalization of their apparent biological complexity. Denaturation studies with avian myeloblastosis virus (AMV) NC reveal approximately 8 kcal/mol of energy stabilizing the native fold of this small protein. Two independent urea-induced structural transitions are detected, by circular dichroism (CD) and intrinsic fluorescence, respectively. These studies suggest that significant structure exists in NCs outside of the highly conserved "cys-his motifs", Cys-X{dollar}{bsol}sb2{dollar}-Cys-X{dollar}{bsol}sb3{dollar}-Gly-His-X{dollar}{bsol}sb4{dollar}-Cys, currently the only regions modeled at atomic resolution. Based on the variety of presumed nucleic acid binding targets, a comprehensive nucleic acid binding study was undertaken to better define and characterize NC participation in the retroviral replication cycle. The nucleic acid affinity of AMV NC, measured by exploiting the anisot ropy of the intrinsic protein fluorescence, is equal (approximately 1 {dollar}{bsol}times{dollar} 10{dollar}{bsol}sp4{dollar} M{dollar}{bsol}sp{lcub}-1{rcub}{dollar} in 125 mM NaCl) for an extensive panel of single- and double-stranded RNA and DNA homopolymers (Gelfand et al, 1993. J. Biol. Chem. 268:18450-18456.). This surprising result suggests that all presumed biological roles for NC are indeed possible. Extension of these results toward a universal NC model required subsequent study of the nucleic acid binding properties of another NC. Binding of equine infectious anemia virus (EIAV) NC to single- and double-stranded homopolymeric nucleic acids substantially alters their intrinsic structures. The complex interaction between EIAV NC and nucleic acids, readily apparent by large transitions in the nucleic acid CD spectra, does not induce melting of double stranded structures. The resulting structures might be the basis for the "stimulatory" roles (e.g., enhancing nucleic acid annealing) attributed to NCs. The structural rearrangement of nucleic acids mediated by the lentiviral EIAV NC is not seen with the "oncoviral" AMV NC. This discrepancy represents the first large difference observed between lentiviral and other retroviral structural proteins, and could have significant impact on the search for anti-AIDS drugs |
Authors
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Gelfand, Craig Alan |
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Contributors
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Publication Detail
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Publisher : Case Western Reserve University / OhioLINK Type : - Format : - |
Date Detail
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2006-08-11 |
Subject
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Chemistry, Biochemistry |
Coverage
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Relation
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Source
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http://rave.ohiolink.edu/etdc/view?acc_num=case1062090926 |
Copyright Information
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unrestricted | Copyright information available at the source archive |
Other Details
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Languages : English |
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