Thermal and Mg2+ dependent behavior of pseudouridines at 39th and 55th of yeast tRNAPhe.
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.
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
D011560:Pseudouridine; D010649:Phenylalanine; D012343:RNA, Transfer; D008274:Magnesium; D014529:Uridine