There are a class of RNA molecules called ribozymes that possess enzymatic activity, meaning they can catalyze chemical reactions. These ribozymes can facilitate their own formation through a process called self-splicing or self-cleaving.
Self-splicing ribozymes are capable of removing their own introns (non-coding regions) through a series of catalytic reactions. One well-known example of a self-splicing ribozyme is the group I intron found in some genes of bacteria and yeast. This ribozyme contains specific sequences that fold into a complex three-dimensional structure, allowing it to catalyze the intron removal reaction without the need for protein enzymes. By catalyzing its own splicing, the ribozyme ensures the production of a functional RNA molecule that can carry out specific cellular functions.
Another example is the hammerhead ribozyme, a small catalytic RNA motif found in some RNA viruses. It can cleave RNA strands at specific sites, again acting as an enzyme without the involvement of proteins. The hammerhead ribozyme is found in the genomes of some RNA viruses and contributes to their replication and survival.
The discovery of these ribozymes challenged the long-held belief that enzymes were exclusively protein-based. It revealed that RNA molecules can also carry out enzymatic functions and catalyze chemical reactions, including their own formation or processing. This concept, known as the RNA world hypothesis, suggests that early forms of life might have relied on RNA as both a genetic material and a catalyst before the emergence of proteins.
how Some RNAs act as enzymes and facilitate their own formation.
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