Question

RECALL What is a ribozyme? List some examples of ribozymes.

Short answer

Ribozymes are RNA molecules capable of catalyzing biochemical reactions. Examples include RNase P, ribosomal RNA, and Group I/II introns.

Step-by-step solution

- Define ribozyme

A ribozyme is a type of RNA molecule that has the ability to catalyze chemical reactions. These molecules are unique because, unlike most biological catalysts that are proteins, ribozymes are composed of RNA.

- Explain the function

Ribozymes perform catalytic activities similar to protein enzymes. They facilitate various biochemical reactions, such as cleaving or ligating RNA strands, and in some cases, can even help synthesize proteins.

- Examples of ribozymes

Some well-known examples of ribozymes include: 1. RNase P - which processes precursor tRNA molecules into their mature form.2. The ribosomal RNA in ribosomes that plays a critical role in protein synthesis. 3. Group I and Group II introns - self-splicing introns found in certain RNA transcripts.

Key concepts

RNA catalysis

RNA catalysis refers to the process by which RNA molecules, known as ribozymes, facilitate chemical reactions. This is an unusual property because most catalysts in biological systems are proteins called enzymes. Ribozymes can accelerate biochemical reactions by lowering the activation energy needed.
Ribozymes can achieve this through their unique three-dimensional structures. These structures enable them to bind to specific substrates and perform functions like cutting RNA strands or assembling them into larger molecules.
This capability is fundamental to various cellular processes. Without RNA catalysis, many essential biochemical reactions would occur too slowly to sustain life.

RNase P

RNase P is a well-known ribozyme that plays an essential role in the maturation of tRNA molecules. tRNA, or transfer RNA, is crucial for protein synthesis in cells. RNase P specifically catalyzes the removal of extra sequences from the precursor tRNA molecules.
By doing this, RNase P transforms precursor tRNA into its mature form, which can then participate in translating genetic information into proteins. Without the action of RNase P, the efficiency and accuracy of protein synthesis would be compromised. The activity of RNase P exemplifies the versatility and necessity of ribozymes in biological processes.

ribosomal RNA

Ribosomal RNA (rRNA) is a key component of ribosomes, the cellular machines that synthesize proteins. rRNA molecules are not just structural elements; they also have catalytic roles. In fact, the ribosome's active site where peptide bonds form between amino acids is catalyzed by rRNA.
Thus, rRNA helps in translating messenger RNA (mRNA) into proteins by facilitating the formation of peptide bonds. This critical function underscores the importance of rRNA as more than just a scaffold but as a vital catalyst in maintaining cellular function and life itself.

self-splicing introns

Self-splicing introns are another fascinating class of ribozymes. Introns are non-coding sequences within RNA transcripts that must be removed for the RNA to become functional. While some introns are removed by protein-based complexes known as spliceosomes, self-splicing introns can catalyze their own removal.
There are two major groups of self-splicing introns: Group I and Group II. Group I introns typically require a guanine nucleotide to initiate the splicing, while Group II introns form a lariat structure during the splicing process.
The ability of these introns to self-splice enables more rapid and flexible RNA processing, highlighting a unique aspect of RNA's catalytic versatility.