Fidelity Mechanisms of the Aminoacyl-tRNA Synthetases

Mascarenhas, Anjali; An, Songon; Rosen, Abbey E.; Martinis, Susan A.; Musier‐Forsyth, Karin

doi:10.1007/978-3-540-70941-1_6

Cited by 65 publications

(104 citation statements)

References 206 publications

Supporting

Mentioning

104

Contrasting

Order By: Relevance

“…To maintain fidelity during protein synthesis, an aaRS thus needs to select the correct amino acid and tRNA substrates from a large pool of structurally similar molecules in the cell. The active-site groove of the aaRS plays a role of the first selection sieve that prevents activation of most noncognate amino acids (3,4), and a cis-editing site (5) or free standing editing domain (6)(7)(8) further proofreads misactivated amino acids. In contrast, the selection of tRNA substrates depends on the ability of aaRSs to establish interactions with a unique set of identity elements present in a given tRNA (9,10).…”

Section: Protein Synthesis | Anticodon Recognitionmentioning

confidence: 99%

Yeast mitochondrial threonyl-tRNA synthetase recognizes tRNA isoacceptors by distinct mechanisms and promotes CUN codon reassignment

Ling

Peterson

Simonović

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Aminoacyl-tRNA synthetases (aaRSs) ensure faithful translation of mRNA into protein by coupling an amino acid to a set of tRNAs with conserved anticodon sequences. Here, we show that in mitochondria of Saccharomyces cerevisiae, a single aaRS (MST1) recognizes and aminoacylates two natural tRNAs that contain anticodon loops of different size and sequence. Besides a regular tRNA Thr 2 with a threonine (Thr) anticodon, MST1 also recognizes an unusual tRNA Thr 1 , which contains an enlarged anticodon loop and an anticodon triplet that reassigns the CUN codons from leucine to threonine. Our data show that MST1 recognizes the anticodon loop in both tRNAs, but employs distinct recognition mechanisms. The size but not the sequence of the anticodon loop is critical for tRNA Thr 1 recognition, whereas the anticodon sequence is essential for aminoacylation of tRNA Thr 2 . The crystal structure of MST1 reveals that, while lacking the N-terminal editing domain, the enzyme closely resembles the bacterial threonyl-tRNA synthetase (ThrRS). A detailed structural comparison with Escherichia coli ThrRS, which is unable to aminoacylate tRNA Thr 1 , reveals differences in the anticodon-binding domain that probably allow recognition of the distinct anticodon loops. Finally, our mutational and modeling analyses identify the structural elements in MST1 (e.g., helix α11) that define tRNA selectivity. Thus, MTS1 exemplifies that a single aaRS can recognize completely divergent anticodon loops of natural isoacceptor tRNAs and that in doing so it facilitates the reassignment of the genetic code in yeast mitochondria.protein synthesis | anticodon recognition

show abstract

Section: Protein Synthesis | Anticodon Recognitionmentioning

confidence: 99%

Yeast mitochondrial threonyl-tRNA synthetase recognizes tRNA isoacceptors by distinct mechanisms and promotes CUN codon reassignment

Ling

Peterson

Simonović

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Although the phenomenon of post-transfer editing in aaRSs is well established, relatively little is known about the detailed hydrolysis mechanism of freestanding editing proteins like YbaK at the molecular level (6,(41)(42)(43)(44). We were especially interested in understanding the basis for the unique Cys-tRNA specificity of YbaK and how discrimination of similar sized ProtRNA is achieved.…”

mentioning

confidence: 99%

Substrate-mediated Fidelity Mechanism Ensures Accurate Decoding of Proline Codons

Kumar

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

Aminoacyl-tRNA synthetases attach specific amino acids to cognate tRNAs. Prolyl-tRNA synthetases are known to mischarge tRNA Pro with the smaller amino acid alanine and with cysteine, which is the same size as proline. Quality control in proline codon translation is partly ensured by an editing domain (INS) present in most bacterial prolyl-tRNA synthetases that hydrolyzes smaller Ala-tRNA Pro Aminoacyl-tRNA synthetases (aaRSs) 3 play a pivotal role in the decoding of genetic information by catalyzing the esterification of cognate amino acids onto specific transfer RNAs (tRNAs) in a two-step reaction (1). The first step involves amino acid activation with ATP to form an aminoacyl-adenylate intermediate and concomitant pyrophosphate release. The second step involves aminoacyl transfer to the cognate tRNA via a transesterification reaction. Although aaRSs display high substrate specificity, they often misactivate structurally similar amino acids. If left unchecked, these mistakes lead to errors in protein synthesis, and accumulation of such errors can be deleterious to cells (2, 3).To ensure high fidelity in translation, aaRSs have evolved several proofreading mechanisms (4 -7). In the first type of proofreading, misactivated aminoacyl-adenylates are enzymatically hydrolyzed or selectively released from the active site followed by solvent hydrolysis, in a process termed "pretransfer" editing. Another mechanism of proofreading known as "posttransfer" editing is generally believed to function via the socalled "double-sieve" mechanism (8). The model predicted that, whereas one active site could not completely discriminate Ile and Val, two separate active sites with distinct strategies for recognition could significantly enhance fidelity. The aminoacylation active site of the aaRS would act as a "coarse" sieve for adenylate synthesis, activating the cognate amino acid but also allowing, to a lesser extent, activation of isosteric or smaller amino acids that could fit into the amino acid binding pocket. The second "fine" sieve would selectively bind misactivated amino acids for editing while excluding the original cognate amino acid. Thus, substrates synthesized in the first sieve would be further screened by the second sieve to enhance fidelity. Subsequently, biochemical and structural data validated this steric exclusion mechanism for valyl-tRNA synthetase and isoleucyl-tRNA synthetase (9, 10). Indeed, members of both classes of synthetases are now known to possess a second active site spatially separated from the ancient catalytic core to carry out post-transfer editing. Structures of class I isoleucyl-tRNA synthetase (10), leucyl-tRNA synthetase (11), and valyl-tRNA synthetase (12) reveal the highly conserved connective peptide 1 domain that functions in editing. Class II alanyl-tRNA synthetase (AlaRS) (13, 14), threonyl-tRNA synthetase (15), prolyltRNA synthetase (ProRS) (16,17), and phenylalanyl-tRNA synthetase (18, 19) also possess distinct domains for post-transfer editing. A recent study of AlaRS revealed an ...

show abstract

“…Each aaRS covalently attaches amino acid to its cognate tRNA to set the genetic code (1,2). Faithful translation in modern cells imposes a great challenge for aaRSs as they select cognate substrate amino acids from a pool of structurally similar amino acids (1,2).…”

mentioning

confidence: 99%

“…Robust editing to achieve proteome fidelity has been commonly thought to be essential to the cell (1,2). Indeed, fidelity can be critical for microbe and mammalian cell viability (3)(4)(5), as well as the prevention of neurological disease (5).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Leucyl-tRNA synthetase editing domain functions as a molecular rheostat to control codon ambiguity in Mycoplasma pathogens

Palencia

Lukk³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Mycoplasma leucyl-tRNA synthetases (LeuRSs) have been identified in which the connective polypeptide 1 (CP1) amino acid editing domain that clears mischarged tRNAs are missing (Mycoplasma mobile) or highly degenerate (Mycoplasma synoviae). Thus, these enzymes rely on a clearance pathway called pretransfer editing, which hydrolyzes misactivated aminoacyl-adenylate intermediate via a nebulous mechanism that has been controversial for decades. Even as the sole fidelity pathway for clearing amino acid selection errors in the pathogenic M. mobile, pretransfer editing is not robust enough to completely block mischarging of tRNA Leu , resulting in codon ambiguity and statistical proteins. A high-resolution X-ray crystal structure shows that M. mobile LeuRS structurally overlaps with other LeuRS cores. However, when CP1 domains from different aminoacyl-tRNA synthetases and origins were fused to this common LeuRS core, surprisingly, pretransfer editing was enhanced. It is hypothesized that the CP1 domain evolved as a molecular rheostat to balance multiple functions. These include distal control of specificity and enzyme activity in the ancient canonical core, as well as providing a separate hydrolytic active site for clearing mischarged tRNA.protein evolution | quality control | statistical proteins | aminoacylation | translation

show abstract

Fidelity Mechanisms of the Aminoacyl-tRNA Synthetases

Cited by 65 publications

References 206 publications

Yeast mitochondrial threonyl-tRNA synthetase recognizes tRNA isoacceptors by distinct mechanisms and promotes CUN codon reassignment

Yeast mitochondrial threonyl-tRNA synthetase recognizes tRNA isoacceptors by distinct mechanisms and promotes CUN codon reassignment

Substrate-mediated Fidelity Mechanism Ensures Accurate Decoding of Proline Codons

Leucyl-tRNA synthetase editing domain functions as a molecular rheostat to control codon ambiguity in Mycoplasma pathogens

Contact Info

Product

Resources

About