Like the L6 protein, L9 also has two domains that are likely involved in 23S rRNA interactions. L9 is the most highly elongated protein of the ribosomal complex with the two domains joined by a by 9-helical-turn connecting region. It is suggested that the spacing involved leads to a function in maintaining the ribosomal activity. Hoffman et al. suggest that L9 serves as a "molecular strut" for ribosomal assembly and activity. The structure above was isolated from Bacillus stearothermophilus via X-ray diffraction and NMR data. (Hoffman et al. 1996)