Molecular model for 5-S RNA. A small-angle x-ray scattering study of native, denatured and aggregated 5-S RNA from Escherichia coli ribosomes.

A tertiary structural model is suggested for Escherichia coli 5-S RNA that consists of one large and two small double helices arranged in the form of the letter Y. This model is consistent with the small-angle X-ray scattering data of native 5-S RNA, measured in the angular range 20 less than or equal to 140 mrad. The radium of gyration is 3.61 +- 0.1 Nm. Denatured 5-S RNA yields a much lower radius of gyration, 2.7 nm, which might indicate that during denaturation one minor double-helical arm of the Y-shaped structure partially collapses into single-stranded areas. At high concentrations (60 mg/ml) of 5-S RNA, the X-ray scattering data indicate that 5-S RNA is aggregated.