Ga. Rocheleau et Sa. Woodson, REQUIREMENTS FOR SELF-SPLICING OF A GROUP INTRON FROM PHYSARUM-POLYCEPHALUM, Nucleic acids research, 22(20), 1994, pp. 4315-4320
The third intron from Physarum polycephalum (Pp LSU 3) is one of the c
losest known relatives to the well-studied Tetrahymena group I intron.
Both introns are located at the same position in the 26S rRNA gene, a
nd with the exception of an open reading frame in Pp LSU 3, are highly
homologous. While Pp LSU 3 has been shown to self splice, little is k
nown about its activity in vitro. We have examined the requirements fa
r self splicing in greater detail. Despite its similarity to the Tetra
hymena intron, Pp LSU 3 is 1500-fold less reactive, demonstrates a pre
ference for high salt, and exhibits a low K-m for GTP. Removal of the
open reading frame results in a modest increase of activity. This syst
em provides an opportunity to understand how sequence variations in tw
o related introns alter the efficiency of autoexcision, and how this r
elates to adaptation of group I introns to their particular sequence c
ontext.