P5abc of the Tetrahymena ribozyme consists of three functionally independent elements.

P5abc domain of Tetrahymena LSU intron functions as an activator that is not essential for but enhances the activity of the ribozyme either when present in cis or when added in trans. This domain contains three regions (A-rich bulge, L5b, and L5c) that have been demonstrated to interact with the rest of the intron. Although these regions are presumably important for efficient activation, the role of each element is not understood in the mechanism of activation. We employed circularly permuted introns and examined the roles of each element. The results show that each of the three elements can activate the intron independently. We also found that a correlation between the activation by P5abc and the physical affinity of P5abc to the intron exists.