Difference between revisions of "Ribozyme"

From Conservapedia
Jump to: navigation, search
(created stub, currently writing article)
 
(saving progress again, still expanding article)
Line 1: Line 1:
A '''ribozyme''' is a [[RNA|polyribonucleotide]] (RNA molecule) with [[enzyme|enzymatic]] activity.  They are sometimes also referred to as "RNA enzymes" however, because this term can lead to some confusion in distinguishing them from [[ribonucleoprotein|ribonucleoproteins]] (proteins that contain RNA), "ribozyme" is preferred.
+
A '''ribozyme''' is a [[RNA|polyribonucleotide]] (RNA molecule) with [[enzyme|enzymatic]] activity.  They are sometimes also referred to as "RNA enzymes" however, to avoid confusion with [[ribonucleoprotein|ribonucleoproteins]] in which the RNA lacks catalytic activity, "ribozyme" is generally preferred.
  
Ribozymes are found in every known cell and are essential to cell functioning.  The most well known example of an essential ribozyme is the 28S rRNA (called the 23S rRNA in [[prokaryotes]]), which carries out the aminoacyltransferase (peptide-lengthening) activity of [[ribosome|ribosomes]].
+
Ribozymes have been found in every known cell and are essential to cell functioning.  The most well known example of an essential ribozyme is the 28S rRNA (called the 23S rRNA in [[prokaryotes]]), which carries out the aminoacyltransferase (peptide-lengthening) activity of [[ribosome|ribosomes]].
 +
 
 +
==Structure and Function==
 +
 
 +
Similar to [[proteins]], RNAs derive their function from their structure.  The ''primary structure'' of an RNA refers to its sequence, which allows the RNA to adopt local conformational structures (e.g. RNA hairpins), these ''secondary structures'' give the RNA molecule an overall ''tertiary structure''.  For RNAs that function in a complex, either with proteins or other RNAs or both, the structure of the complex is called ''quaternary structure''.
 +
 
 +
The catalytic site (or sites) of a ribozyme function in a similar manner to the active sites of protein [[enzyme|enzymes]].  They lower the ΔG‡ ([[Gibbs energy]]) of a chemical reaction by binding to the substrates in a manner that makes the reaction more energetically favorable.  Also like protein enzymes, many ribozymes require [[cofactors]] (e.g. Mg<sup>2+</sup>) in order to function properly.
 +
 
 +
==Examples==
 +
 
 +
===28S rRNA===
 +
 
 +
The '''28S rRNA''' (the 23S rRNA in [[prokaryotes]]) is a [[rRNA|ribosomal RNA]].  It is the part of the ''large subunit'' of a [[ribosome]] that catalyzes [[peptide bond]] formation between amino acids during protein synthesis.
 +
 
 +
Notably, the antibiotic [[chloramphenicol]] works by inhibiting the aminoacyltransferase activity of the bacterial 23S rRNA.
 +
 
 +
===Self-splicing introns===
 +
 
 +
Self-splicing [[introns]] in a nascent RNA transcript are ribozymes that excise themselves without the need for [[splicosome|splicosomal]] machinery.
 +
 
 +
Although self-splicing introns are relatively rare in [[eukaryote|eukaryotic]] genes, they are the only types of introns found in the few bacterial protein-coding genes that contain introns.  Self-splicing introns appear to have originated in ancient [[retrovirus|retroviruses]].  Furthermore, the remarkable sequence homology between bacterial and eukaryotic self-splicing introns is considered a major piece of evidence for the common origin of introns in both clades.
 +
 
 +
===RNase P===

Revision as of 19:20, 1 November 2012

A ribozyme is a polyribonucleotide (RNA molecule) with enzymatic activity. They are sometimes also referred to as "RNA enzymes" however, to avoid confusion with ribonucleoproteins in which the RNA lacks catalytic activity, "ribozyme" is generally preferred.

Ribozymes have been found in every known cell and are essential to cell functioning. The most well known example of an essential ribozyme is the 28S rRNA (called the 23S rRNA in prokaryotes), which carries out the aminoacyltransferase (peptide-lengthening) activity of ribosomes.

Structure and Function

Similar to proteins, RNAs derive their function from their structure. The primary structure of an RNA refers to its sequence, which allows the RNA to adopt local conformational structures (e.g. RNA hairpins), these secondary structures give the RNA molecule an overall tertiary structure. For RNAs that function in a complex, either with proteins or other RNAs or both, the structure of the complex is called quaternary structure.

The catalytic site (or sites) of a ribozyme function in a similar manner to the active sites of protein enzymes. They lower the ΔG‡ (Gibbs energy) of a chemical reaction by binding to the substrates in a manner that makes the reaction more energetically favorable. Also like protein enzymes, many ribozymes require cofactors (e.g. Mg2+) in order to function properly.

Examples

28S rRNA

The 28S rRNA (the 23S rRNA in prokaryotes) is a ribosomal RNA. It is the part of the large subunit of a ribosome that catalyzes peptide bond formation between amino acids during protein synthesis.

Notably, the antibiotic chloramphenicol works by inhibiting the aminoacyltransferase activity of the bacterial 23S rRNA.

Self-splicing introns

Self-splicing introns in a nascent RNA transcript are ribozymes that excise themselves without the need for splicosomal machinery.

Although self-splicing introns are relatively rare in eukaryotic genes, they are the only types of introns found in the few bacterial protein-coding genes that contain introns. Self-splicing introns appear to have originated in ancient retroviruses. Furthermore, the remarkable sequence homology between bacterial and eukaryotic self-splicing introns is considered a major piece of evidence for the common origin of introns in both clades.

RNase P