GROUP III INTRON Meaning and
Definition
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A group III intron is a type of intron that is commonly found in bacterial and organellar genomes. Introns are non-coding sequences of DNA or RNA that are transcribed but are later removed during the process of splicing. Group III introns are self-splicing, meaning they can catalyze the splicing process without the aid of any additional protein factors.
Group III introns are characterized by their distinct secondary structure, which includes six conserved regions (C1-C6) and three stem-loop domains (P1-P3). The function of these introns is to remove themselves from the precursor RNA molecule and ligate the two flanking exons together, thus preserving the integrity of the coding sequence.
The splicing of group III introns involves a series of RNA structural rearrangements known as conformational changes. These conformational changes are facilitated by the interaction of the intron with a guanosine nucleotide, which acts as a co-factor. In addition to splicing themselves, group III introns have been found to possess RNA-cleaving and RNA-binding activities, suggesting additional roles beyond self-splicing.
Group III introns are evolutionarily ancient and have diversified into different subgroups based on their structural and functional characteristics. They have been observed in various bacterial species, as well as in organelles such as mitochondria and chloroplasts. Studies on group III introns have provided valuable insights into the mechanisms of RNA splicing and have implications for understanding the evolution of genetic information processing systems.
