Artificial modules for enhancing rate constants of a Group I intron ribozyme without a P4-P6 core element.

In this paper we report newly selected artificial modules that enhance the kcat values comparable with or higher than those of the wild-type ribozyme with broad substrate specificity. The elements required for the catalysis of Group I intron ribozymes are concentrated in the P3-P7 domain of their core region, which consists of two conserved helical domains, P4-P6 and P3-P7. Previously, we reported the in vitro selection of artificial modules residing at the peripheral region of a mutant Group I ribozyme lacking P4-P6. We found that derivatives of the ribozyme containing the modules performed the reversal of the first step of the self-splicing reaction efficiently by using their affinity to the substrate RNA, although their kcat values and substrate specificity were uninfluenced and limited, respectively. The results show that it is possible to add a variety of new domains at the peripheral region that play a role comparable with that of the conserved P4-P6 domain.