Nonintercalative binding of ethidium bromide to nucleic acids: crystal structure of an ethidium--tRNA molecular complex.

X-ray diffraction studies at 4.5-A resolution on crystals of a complex of ethidium bromide and yeast phenylalanine tRNA reveal a nonintercalative model of binding of the ethidium within the tertiary structure. This is contrary to the expected interacalative binding to the double-helical regions.