418 Chapter 10
Figure 10.21 RNA-binding rings in all three taxonomic domains of life. (a) The trp RNA-binding attenuation
protein bound to single-stranded RNA (PDB: 1C9S). Here the RNA is bound around the
circumference of the ring. (b) In contrast the hexameric Af-Sm1 protein from the archaebacterium
Archaeoglobus fulgidus forms a complex with short poly-U RNA in its central channel (PDB: 1I5L).
A homologous protein is found in eukaryotes