title: Thermal and Mg2+ dependent behavior of pseudouridines at 39th and 55th of yeast tRNAPhe.
abstract: Pseudouridine psi 55 alone and both psi 55 and psi 39 in yeast tRNAPhe are selectively modified with fluorescent reagent of 4-bromomethyl-7-methoxycoumarin (BMC). The change of fluorescence intensity was measured as a function of temperature and Mg2+ concentration. Fluorescent quenching shows the stacked and unstacked forms of Y base, dependent on Mg2+ concentration. In contrast, Mg2+ had no effect on psi 55-BMC in T psi C loop at 20 degrees C. Fluorescence on titrating Mg2+ exhibited a kind of Mg2+-induced structural collapse at the corner of L-structure. The melting of psi 55-BMC takes place at 70 degrees C in 10mM Mg2+. At very low Mg2+ concentration, melting takes place at 35 degrees C. The melting of psi 39-BMC, located near the anticodon loop, was observed before the unfolding of the whole structure of tRNAPhe. A conformational transition of the anticodon loop takes place at a lower temperature and it is also expected in the quenching experiment of Y base.
mesh_terms: D006358:Hot Temperature; D008274:Magnesium; D009690:Nucleic Acid Conformation; D010649:Phenylalanine; D011560:Pseudouridine; D012343:RNA, Transfer; D012440:Saccharomyces / Q000032:analysis; D013050:Spectrometry, Fluorescence; D014529:Uridine / Q000031:analogs & derivatives
chemical_list: D011560:Pseudouridine; D010649:Phenylalanine; D012343:RNA, Transfer; D008274:Magnesium; D014529:Uridine