Question

Механизм терминации трансляции

Answer 1

Секвенируя цепь мРНК по триплетам и соответственно удлиняя полипептидную цепь, транслирующая рибосома доходит до конца кодирующей последовательности и встречается с одним из трех триплетов ,не кодирующих аминокислоты и обозначаемых как стоп-кодоны, или кодоны терминации – UAG, UAA или UGA.В результате завершающей транслокации полипетидил-тРНК оказывается связанной с последним значащим триплетом в Р-участке рибосомы, а в А-участке устанавливается кодон терминации. В клетке нет аминоцил-т-РНК ,способных комплементарно связываться с терминирующим кодоном, и потому А-участок не заполняется обычным акцепторным субстратом ,каковым является аминоацил-тРНК. Вместо этого в дело вступают специальные белки ,называемые факторми терминации , или факторами освобождения. Один из них, RF1 , взаимодействует непосредственно с кодоном терминации в А-участке, а другой,RF3 ,при содействии первого и с участием ГТФ – с большей субчастицей рибосомы .Результатом связывания этих факторов с рибосомой происходят реакции ,приводящие к отделению вновь синтезированной мРНК из рибосомы.

Answer 2

Mechanism of Translation Termination

The termination of translation is a crucial step in protein synthesis, where the ribosome recognizes the stop codon on the mRNA and releases the newly synthesized polypeptide chain. The mechanism of translation termination involves several key components and processes.

1. Stop Codons: Translation termination is initiated when the ribosome encounters a stop codon on the mRNA. There are three stop codons: UAA, UAG, and UGA. These codons do not code for any amino acids but act as signals for the termination process.

2. Release Factors (RFs): Release factors are proteins that recognize the stop codons and facilitate the termination of translation. In prokaryotes, two release factors, RF1 and RF2, are responsible for recognizing the stop codons UAA/UAG and UAA/UGA, respectively. In eukaryotes, a single release factor, eRF1, recognizes all three stop codons.

3. GTP Hydrolysis: During translation termination, GTP hydrolysis plays a crucial role. GTP-bound release factors bind to the ribosome when a stop codon is encountered. GTP hydrolysis triggers a conformational change in the ribosome, leading to the release of the polypeptide chain.

4. Ribosome Recycling: After the termination of translation, the ribosome needs to be recycled for further rounds of protein synthesis. Ribosome recycling factors, such as RRF (ribosome recycling factor) in prokaryotes and ABCE1 (ATP-binding cassette subfamily E member 1) in eukaryotes, dissociate the ribosome from the mRNA and tRNA, allowing the ribosome to be reused.

5. mRNA Degradation: Once translation termination occurs, the mRNA molecule may undergo degradation. This ensures that the mRNA is not used for further translation and helps regulate gene expression.

It is important to note that the mechanism of translation termination can vary between prokaryotes and eukaryotes. The specific details and factors involved may differ slightly. Additionally, the termination process can be influenced by various regulatory factors and mechanisms.

Please let me know if you have any#### Mechanism of Translation Termination

The termination of translation is an essential step in protein synthesis, where the ribosome recognizes the stop codon on the mRNA and releases the newly synthesized protein. The mechanism of translation termination involves several key components and processes.

1. Stop Codons: Translation termination is initiated when the ribosome encounters a stop codon on the mRNA. There are three stop codons: UAA, UAG, and UGA. These codons do not code for any amino acids but serve as signals for the ribosome to stop protein synthesis.

2. Release Factors (RFs): Release factors are proteins that recognize the stop codons and promote the termination of translation. In bacteria, two release factors are involved: RF1 and RF2. RF1 recognizes the UAA and UAG stop codons, while RF2 recognizes the UAA and UGA stop codons. In eukaryotes, eRF1 is the main release factor responsible for recognizing all three stop codons.

3. GTP Hydrolysis: During translation termination, GTP hydrolysis is required for the release of the newly synthesized protein. GTP hydrolysis is catalyzed by the release factors and is essential for the dissociation of the ribosome from the mRNA.

4. Ribosome Recycling: After the termination of translation, the ribosome needs to be recycled for further rounds of protein synthesis. This process involves the dissociation of the ribosome subunits and the release of the mRNA and tRNA molecules. Several factors, such as Rho (in bacteria) and ABCE1 (in eukaryotes), are involved in ribosome recycling.

The exact details of the mechanism of translation termination can vary between prokaryotes and eukaryotes. In prokaryotes, the release factors RF1 and RF2 recognize the stop codons, leading to the hydrolysis of GTP and the release of the newly synthesized protein. In eukaryotes, eRF1 recognizes the stop codons and promotes the release of the protein.

It's important to note that the information provided above is based on search results from You.com. For more detailed and comprehensive information, it is recommended to refer to reliable sources on molecular biology and protein synthesis.