Specificity of TRAP-RNA interactions: crystal structures of two complexes with different RNA sequences

X-ray structures of TRAP bound to 53-nucleotide single-stranded RNA containing GAGUU and GAGCC repeats were determined. Comparison of these structures with that of TRAP bound to RNAs containing GAGAU repeats gives insight into the specificity of the TRAP-RNA interaction and suggests that pyrimidine spacer nucleotides bind more strongly owing to the greater increase in entropy upon binding.