Name: catalytic rna: ribozymes in action
Uploaded: 2023-04-30T18:28:42.000Z
Duration: 2 min 47 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.2

Ribozymes

Ribozyme sind spezielle Arten von RNA, die als Enzyme fungieren können. 
Die Substrate für die meisten natürlich vorkommenden Ribozyme sind RNA-Phosphodiesterbindungen. Die einzige bekannte Ausnahme ist die ribosomale RNA 23S im bakteriellen Ribosom, die die Bildung von Peptidbindungen katalysiert.
Ribozyme wurden in allen Arten von Organismen gefunden und ähneln proteinbasierten Enzymen, da beide die Reaktionsgeschwindigkeit erhöhen. Viele Ribozyme benötigen Metallionen, wie Magnesium, als Co-Faktoren, um Reaktionen zu katalysieren.
Einige Klassen von Introns können als Ribozyme fungieren. Introns werden in fünf verschiedene Klassen eingeteilt: nukleäre mRNA, nukleare tRNA, Archaeen, Introns der Gruppe eins und Gruppe zwei.
Introns der Gruppen eins und zwei sind große Ribozyme, die mehrere hundert Nukleotide lang sind und in Pilz- und Pflanzenmitochondrien, Chloroplasten, Bakteriophagen und eukaryotischen Viren vorkommen. 
Sie können sich ohne die Hilfe von Proteinen selbst spleißen, während nukleäre Introns durch das Spleißosom, einen RNA- und Protein-haltigen Enzymkomplex, gespleißt werden. 
Kleine Ribozyme sind in der Regel 50 bis 150 Nukleotide lang und sind selbstspaltende Nukleotidsequenzmotive. Diese sind in vielen RNA-Pflanzenviren sowie im Hepatitis-Delta-Virus, einem menschlichen Krankheitserreger, zu finden. 
Der Replikationsprozess in diesen Viren produziert lange RNA, die mehrere Einheiten des viralen Genoms trägt, wobei jede Einheit ein kleines Ribozym wie einen Hammerhai trägt. Diese Hammerhai-Enzyme in regelmäßigen Abständen durchlaufen eine Selbstspaltung, die zu einem Bruch der langen RNA in einzelne Genomsegmente führt.
Die meisten Ribozyme spalten ihre eigene Nukleotidsequenz, Ribonuklease P kann jedoch auch andere RNA-Moleküle spalten. Ribonuklease P kommt in einigen Bakterien vor und verarbeitet Vorläufer-tRNA, um ein reifes 5'-Ende zu erzeugen.
Es ist bekannt, dass die natürlich verfügbaren Ribozyme einen engen Bereich von Reaktionen katalysieren, wie z. B. den Phosphoryltransfer in Nukleinsäuren und die Bildung von Peptidbindungen in Proteinen. Wissenschaftler haben im Labor künstliche Ribozyme synthetisiert, die eine Vielzahl von Reaktionen wie die Bildung von Kohlenstoff-Kohlenstoff-Bindungen und Oxidations-Reduktions-Reaktionen durchführen können.

<ol>
	<li>Doherty, Elizabeth A. und Jennifer A. Doudna. "Ribozym-Strukturen und -Mechanismen." Annual Review of Biophysics and Biomolecular Structure 30, Nr. 1 (2001): 457-475.</li>
	<li>Weinberg, Christina E., Zasha Weinberg und Christian Hammann. "Neuartige Ribozyme: Entdeckung, katalytische Mechanismen und das Bestreben, die biologische Funktion zu verstehen." Nukleinsäureforschung 47, Nr. 18 (2019): 9480-9494. </li>
	<li>Ferré-D'Amaré, Adrian R. und William G. Scott. "Kleine selbstspaltende Ribozyme." Cold Spring Harbor Perspectives in Biology 2, Nr. 10 (2010): a003574.</li>
	<li>Tanner, N. Kyle. "Ribozyme: die Eigenschaften und Eigenschaften katalytischer RNAs." FEMS Microbiology Reviews 23, Nr. 3 (1999): 257-275.</li>
</ol>

ribozyme

Der Begriff Ribozym wird für RNA verwendet, die als Enzym wirken kann. Ribozyme finden sich hauptsächlich in ausgewählten Viren, Bakterien, Pflanzenorganellen und niederen Eukaryoten. Ribozyme wurden erstmals 1982 entdeckt, als das Labor von Tom Cech beobachtete, dass Gruppe-I-Introns als Enzyme wirken. Kurz darauf folgte die Entdeckung eines weiteren Ribozyms, der Ribonuklease P, durch das Labor von Sid Altman. Sowohl Cech als auch Altman erhielten 1989 den Nobelpreis für Chemie für ihre Arbeiten an Ribozymen.

Ribozyme können je nach ihrer Größe in zwei Gruppen eingeteilt werden – große und kleine. Große Ribozyme variieren in der Größe von einigen hundert bis zu mehreren tausend Nukleotiden. Die Typ-I- und Typ-II-Introns sowie die bakterielle Ribonuklease P sind große Ribozyme. Kleine Ribozyme sind 30 bis 150 Nukleotide lang. Sie kommen in vielen pathogenen Pflanzenviren und dem Hepatitis-Delta-Virus (HDV), einem menschlichen Pathogen, vor. Hammerhead, Haarnadel, HDV und Varkud-Satellit sind gängige Arten von kleinen Ribozymen. Die meisten großen Ribozyme benötigen Metallionen, insbesondere Mg2+, für ihre Aktivität, während Metallionen für die meisten kleinen Ribozyme nicht notwendig sind. Das glmS-Ribozym, im glmS-mRNA, ist ein einzigartiges a-Ribozym, da es auch als Riboschalter wirkt, wenn Glucosamin-6-phosphat in hohen Konzentrationen vorhanden ist.

Die meisten natürlich vorkommenden Ribozyme katalysieren die Selbstspaltung, indem sie Phosphodiesterbindungen in ihrer eigenen RNA brechen. Im Gegensatz zu einem typischen Proteinenzym führen die meisten Ribozyme eine Einzelumsatzreaktion durch, da sie nach der Selbstspaltung nicht mehr aktiv sind. Jedoch führen zwei Ribozyme - die Ribonuklease P und die 23S-RNA in der 50S-ribosomalen Untereinheit - unterschiedliche Reaktionen durch. Die bakterielle Ribonuklease P ist ein RNA-Proteinkomplex, der Endonuklease-Aktivität besitzt und Mg2+-Ionen benötigt. Ihre RNA-Komponente wirkt auf das 5'-Ende der unreifen tRNA, um das reife 5'-Ende zu produzieren. Die in den Ribosomen vorhandene 23S-RNA unterscheidet sich von allen anderen bekannten natürlichen Ribozymen, da sie anstelle von Phosphoryltransferreaktionen Peptidbindungsreaktionen während der Translation durchführt.

Da RNA sowohl als Träger genetischer Informationen als auch als Enzyme wirken kann, wird die Hypothese aufgestellt, dass in der Vergangenheit eine „RNA-Welt“ existiert haben könnte, in der RNA eine wichtige Rolle bei der Entwicklung der frühen Lebensformen spielte. Mit der Evolution komplexer Lebensformen könnten jedoch Proteine mit zwanzig Aminosäuren begonnen haben, als Enzyme zu wirken und übernahmen viele der durch Ribozyme durchgeführten Reaktionen. Diese Theorie wird durch die in-vitro entwickelten künstlichen Ribozyme unterstützt, die eine Vielzahl von Reaktionen wie Amidbindungsbildung, glykosidische Bindungsbildung, Kohlenstoff-Kohlenstoff-Bindungsbildung und Oxidations-Reduktions-Reaktionen durchführen können.

Ribozyme

Der Begriff Ribozym wird für RNA verwendet, die als Enzym fungieren kann. Ribozyme kommen hauptsächlich in ausgewählten Viren, Bakterien, Pflanzenorganellen und ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Energy and Catalysis

Energie und Katalyse

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

catalytic rna: ribozymes in action

Ribozymes are RNA molecules that can act as enzymes. They help speed up specific chemical reactions without being protein enzymes. This makes them an important example of RNA with more than one job in the cell.

Some ribozymes can cut RNA molecules, and others can join them together. This shows that RNA can do catalytic work as well as carry genetic information. Ribozymes are a key part of how scientists think about the many roles of RNA in biology.

One well-known ribozyme is ribonuclease P, or RNase P. It helps process precursor tRNA into mature tRNA by removing extra RNA at one end. This process is important because tRNA must be correctly trimmed before it can function in protein synthesis.

Catalytic RNA: Ribozymes in Action

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Explore ribozymes, RNA molecules that act as enzymes, cut or join RNA, and help process precursor tRNA into mature tRNA for protein synthesis.

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Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.c

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.4

SC.912.L.18.11

Texas Essential Knowledge and Skills

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BIO.11.B

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LS.Bio.1.1

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Catalytic RNA: Ribozymes in Action

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