title: Evidence for stacking interactions between 5-mercurated polyuridylic acid and HIV-1 p7 nucleocapsid protein obtained by phosphorescence and optically detected magnetic resonance (ODMR).
abstract: The photoexcited triplet state of Trp-37 in the C-terminal zinc finger of the HIV-1 p7 nucleocapsid protein was used as a probe of p7 interactions with the heavy atom-derivatized RNA homopolymer, poly-5-mercuriuridylic acid (5-HgU). Binding of p7 to 5-HgU (Hg blocked with 2-mercaptoethanol) produces an external heavy atom effect (HAE) on Trp-37 characterized by fluorescence quenching, reduction of the phosphorescence lifetime by three orders of magnitude, and the appearance of the D+E phosphorescence-detected ODMR signal, absent in unperturbed Trp, but induced by a HAE. The details of the HAE are consistent with out-of-plane van der Waals contact of Hg with the indole chromophore of Trp-37. Steric requirements suggest further that the Trp-RNA contact occurs via an aromatic stacking interaction.
authors.affiliation: Department of Chemistry, University of California, Davis 95616.
authors.forename: W C
authors.initials: WC
authors.lastname: Lam
authors.forename: A H
authors.initials: AH
authors.lastname: Maki
authors.forename: J R
authors.initials: JR
authors.lastname: Casas-Finet
authors.forename: J W
authors.initials: JW
authors.lastname: Erickson
authors.forename: R C
authors.initials: RC
authors.lastname: Sowder
authors.forename: L E
authors.initials: LE
authors.lastname: Henderson
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins; D015683:Gene Products, gag / Q000737:chemistry / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism; D049449:Luminescence; D008279:Magnetic Resonance Imaging; D008969:Molecular Sequence Data; D011072:Poly U / Q000737:chemistry / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism; D014764:Viral Proteins; D016335:Zinc Fingers / Q000502:physiology; D054301:gag Gene Products, Human Immunodeficiency Virus
chemical_list: D036022:Capsid Proteins; D015683:Gene Products, gag; C071884:NCP7 protein, Human immunodeficiency virus 1; D012367:RNA, Viral; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; D011072:Poly U; C053361:poly-5-mercuriuridylic acid; D014364:Tryptophan