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Evidence for stacking interactions between 5‐mercurated polyuridylic acid and HIV‐1 p7 nucleocapsid protein obtained by phosphorescence and optically detected magnetic resonance (ODMR)
Author(s) -
Lam Wai-Chung,
Maki August H.,
Casas-Finet José R.,
Erickson John W.,
Sowder Raymond C.,
Henderson Louis E.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80962-t
Subject(s) - phosphorescence , chemistry , stacking , steric effects , chromophore , tryptophan , fluorescence , quenching (fluorescence) , photochemistry , förster resonance energy transfer , stereochemistry , crystallography , biophysics , biochemistry , amino acid , biology , organic chemistry , physics , quantum mechanics
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.