Group I and group II introns.

Abstract

Group I and group II introns are two types of RNA enzymes, ribozymes, that catalyze their own splicing by different mechanisms. In this review, we summarize current information about the structures of group I and group II introns, their RNA-catalyzed reactions, the facilitation of RNA-catalyzed splicing by protein factors, and the ability of the introns to function as mobile elements. The RNA-based enzymatic reactions and intron mobility provide a framework for considering the role of primordial catalytic RNAs in evolution and the origin of introns in higher organisms.

Slow evolution of 1506 group I intron in Spirogyra Link 1820 (Zygnematophyceae, Streptophyta), a fast evolving lineage in the Zygnemataceae.

“…The introns show most features of the characteristic catalytic cores for enzymatic activity consisting of P3, P4, J4/5, P6, P7, P8 and P9 which are highly conserved (Saldanha et al 1993). They also exhibit typical linker regions J3/4: AAC, J6/7: UCA, J8/7: AAGAUA (GaneSan & KeSavan 2009).…”

“…Introns are of interest because they are used to gain insight into the evolution of protein synthesis and how primitive RNAs could have catalyzed their own replication (Saldanha et al 1993). Beside group I introns, group II intron and spliceosomal introns exist, which are defined by their way of splicing (self-splicing vs. RNA operated splicing) and have a distinct secondary structure (Saldanha et al 1993).…”

“…Introns are of interest because they are used to gain insight into the evolution of protein synthesis and how primitive RNAs could have catalyzed their own replication (Saldanha et al 1993). Beside group I introns, group II intron and spliceosomal introns exist, which are defined by their way of splicing (self-splicing vs. RNA operated splicing) and have a distinct secondary structure (Saldanha et al 1993). Group I introns are an important class of RNA enzymes that also exhibit a typical secondary structure that is expressed in the sub-domains P1-P9 and the conserved core regions P, Q, R and S (Burke et al 1987;CeCh 1988).…”

Crystallization and preliminary diffraction analysis of a group I ribozyme from bacteriophage Twort

“…A group I self-splicing intron contains an active site that allows it to excise itself from a precursor RNA and ligate the¯anking exons, generating an intact mRNA, tRNA or rRNA (Cech, 1993;Kruger et al, 1982;Saldanha et al, 1993). This self-splicing reaction requires only suf®cient magnesium ions ($2 mM) to fold the RNA and a guanosine-nucleoside substrate (Cech, 1993;Kruger et al, 1982;Saldanha et al, 1993).…”

“…This self-splicing reaction requires only suf®cient magnesium ions ($2 mM) to fold the RNA and a guanosine-nucleoside substrate (Cech, 1993;Kruger et al, 1982;Saldanha et al, 1993).…”