title: Mg2+-induced variations in the conformation and dynamics of HIV-1 TAR RNA probed using NMR residual dipolar couplings.
abstract: The effects of divalent Mg(2+) on the conformation and dynamics of the stem-loop transactivation response element (TAR) RNA from HIV-1 have been characterized using NMR residual dipolar couplings (RDCs). Order matrix analysis of one bond 13C-1H RDCs measured in TAR at [Mg(2+)]:[TAR] stoichiometric ratios of approximately 3:1 (TAR(3.0Mg)) and approximately 4.5:1 (TAR(4.5Mg)) revealed that Mg(2+) reduces the average inter-helical angle from 47(+/-5) degrees in TAR(free) to 5(+/-7) degrees in TAR(4.5Mg). In contrast to the TAR(free) state, the generalized degree of order for the two stems in TAR(4.5Mg) is found to be identical within experimental uncertainty, indicating that binding of Mg(2+) leads to an arrest of inter-helical motions in TAR(free). Results demonstrate that RDC-NMR methodology can provide new insight into the effects of Mg(2+) on both the conformation and dynamics of RNA.
authors.affiliation: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. hashimi@umich.edu
authors.forename: Hashim M
authors.initials: HM
authors.lastname: Al-Hashimi
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Pitt
authors.forename: Ananya
authors.initials: A
authors.lastname: Majumdar
authors.forename: Weijun
authors.initials: W
authors.lastname: Xu
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
mesh_terms: D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012367:RNA, Viral / Q000737:chemistry* / Q000378:metabolism; D012996:Solutions
chemical_list: D012367:RNA, Viral; D012996:Solutions; D008274:Magnesium