Transfer RNA (tRNA) synthetases are enzymes that attach a specific amino acid to its corresponding tRNA for protein biosynthesis at the ribosome. Organisms use up to 20 tRNA synthetases to generate aminoacyl-tRNAs, one for each of the 20 standard amino acids. While all tRNA synthetases carry out the same fundamental chemistry, they are distinguished by their structure, regulation, and often by novel functions outside their canonical role in protein biosynthesis. Given their essential role in cellular metabolism, even minor defects in function can result in disease; the tRNA synthetases are also of interest in the development of novel drugs.
ARSs catalyze the esterification of amino acids to the 3-terminus of cognate tRNAs bearing the correct anticodon triplet to ensure accurate information transfer from mRNA to protein according to the rules of the genetic code [1,2]. Class I and II ARSs can be further grouped into subclasses based on additional structural features and their recognition of related amino acid substrates.
Several ARSs, including LeuRS, IleRS, ValRS, AlaRS, and GluProRS (EPRS), contain a separate editing domain for hydrolyzing mis-aminoacylated products to maintain translation fidelity [4,5]. Miscoding, or the insertion of incorrect amino acids into the nascent chain at a given codon, changes the primary sequence of a peptide, potentially altering its structure and function. Typically, 20 aaRSs are encoded in cells (exceptions exist ), each responsible for activating and transferring one amino acid onto cognate tRNA isoacceptors.
In this example, Enterococcus faecalis ProRS (PDB ID: 2J3L, represented as a monomer for simplicity)  binds proline and catalyzes formation of the activated prolyl-adenylate, releasing inorganic pyrophosphate. Once the incorrect amino acid has been activated forming an aminoacyl-adenylate (AA-AMP), pre-transfer editing pathways will hydrolyze AA-AMP either in the presence (tRNA-dependent, not shown) or absence (tRNA-independent) of tRNA (PDB ID: 6UGG) .
Which of the following catalyzes the attachment of amino acids to tRNA?
Aminoacylation, the attachment of an amino acid to a tRNA, is typically a two-step process catalyzed by aminoacyl-tRNA synthetases (aaRSs). The first step, termed “activation”, is the formation of an aminoacyl-AMP (aminoacyl-adenylate) on the enzyme through the hydrolysis of adenosine triphosphate (ATP).
How does an amino acid attach to tRNA?
A tRNA with the complementary anticodon is attracted to the ribosome and binds to this codon. The tRNA carries the next amino acid in the polypeptide chain. The first tRNA transfers its amino acid to the amino acid on the newly arrived tRNA, and a chemical bond is made between the two amino acids.
Which enzyme catalyzes the attachment of a specific amino acid to the correct tRNA multiple choice question?
The activation reaction is catalyzed by specific aminoacyl-tRNA synthetases, which are also called activating enzymes. The first step is the formation of an aminoacyl adenylate from an amino acid and ATP.
|What determines which base is to be added to an RNA strand during transcription?||Base pairing between the DNA template strand and the RNA nucleotides|
Don’t know Remaining cards (0)
QuestionAnswerWhat name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?TranscriptionWhat name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?TranslationWhat name is given to the process in which pre-mRNA is edited into mRNA?RNA processingPolypeptides are assembled from ______.amino acidsRNA processing converts the RNA transcript into _____.mRNAThe direction of synthesis of an RNA transcript is ______.5′ -> 3′What is the process called that converts the genetic information stored in DNA to an RNA copy?TranscriptionDNA does not store the information to synthesize which of the following?OrganellesTranscription begins at a promoter. What is a promoter?A site in DNA that recruits the RNA PolymeraseWhich of the following statements best describes the promoter of a protein-coding gene?The promoter is a nontranscribed region of a gene.What determines which base is to be added to an RNA strand during transcription?Base pairing between the DNA template strand and the RNA nucleotidesWhich of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?ComplementaryWhat happens to RNA polymerase II after it has completed transcription of a gene?It is free to bind to another promoter and begin transcriptionDuring RNA processing a(n) _____ is added to the 3′ end of the RNA.a long string of adenine nucleotidesDuring RNA processing a(n) _____ is added to the 5′ end of the RNA.modified guanine nucleotideSpliceosomes are composed of ______.snRNPs and other proteinsThe RNA segments joined to one another by spliceosomes are ______.exonsTranslation occurs in the _____.cytoplasmWhere does translation take place?RibosomeWhich nucleic acid is translated to make a protein?mRNAWhich of the following processes is an example of a post-translational modification?PhosphorylationWhich of the following steps occurs last in the initiation phase of translation?The large ribosomal subunit joins the complexAt which site do new aminoacyl tRNAs enter the ribosome during elongationA-siteWhat is meant by translocation?The ribosome slides on codon down the mRNATrue or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.FalseWhat enzyme catalyzes the attachment of an amino acid to tRNA?aminoacyl-tRNA synthetaseThe tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.CUGThe initiator tRNA attaches at the ribosome’s _____ site.PTrue or false?
A codon is a group of three bases that can specify more than on amino acid.FalseWhich of the following statements about mutations is false?A knock-out mutation results in a total absence of the mutated protein.If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?DeletionWhich mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?One addition and one deletion mutationIf the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?TwoIf a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?An addition mutation and a deletion mutationFor any given gene, what ultimately determines which DNA strand serves as the template strand?the base sequence of the gene’s promoter