The 23S rRNA gene of Chlamydomonas reinhardtii contains a group IA3 intron, Cr.LSU, whose splicing is essential for cell growth. To better understand Cr.LSU splicing, kinetic analyses were undertaken with 23S.3, a preRNA previously shown to self-splice. Self-splicing of 23S.3 showed biphasic kinetics, with only ~ 33% reacting efficiently. Removal of a region of the 5' exon that could potentially interfere with the intron core (i.e. P3) increased the size (53%) of the active fraction. Replacement of the large P6a-extension by a 20-nt stem-loop further increased the active fraction to ~ 80%. The k(cat) and K(M)(G) for self-splicing (first step) by these latter RNAs were ~ 1 min-1 and ~ 20 μM, respectively. These results indicate that Cr.LSU is a highly efficient ribozyme whose folding in vitro is impeded by exonic and/or intronic sequences. The implications for in vivo splicing of Cr.LSU are discussed. (C) 2000 Academic Press.
|頁（從 - 到）||967-971|
|期刊||Biochemical and Biophysical Research Communications|
|出版狀態||已發佈 - 7月 14 2000|
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