ANKRD16 (ankyrin repeat domain-containing 16) is a vertebrate-specific protein of nine ankyrin repeats that safeguards the fidelity of alanyl-tRNA synthetase (AlaRS, AARS1). It binds the AlaRS catalytic domain directly and accepts serine that AlaRS has misactivated onto its own lysine side chains (Lys102, Lys135 and Lys165 in mouse, all conserved in human), so the seryl-adenylate is consumed before serine can be charged onto tRNA(Ala). It acts before tRNA charging and does not deacylate mischarged Ser-tRNA(Ala). In mice, loss of ANKRD16 alone is tolerated, but in an AlaRS editing-defective background it causes protein aggregation and neuron loss, and complete loss in that background is embryonic lethal. It is cytoplasmic and also nuclear.
Definition: Accepting the aminoacyl group of a non-cognate aminoacyl-adenylate formed by an aminoacyl-tRNA synthetase onto a residue of the acceptor protein, so that the misactivated amino acid is not transferred to tRNA.
Justification: ANKRD16 neither hydrolyses mischarged tRNA nor acts as a deacylase; it accepts misactivated serine from AlaRS onto its own lysines. No GO molecular function describes a protein acting as the acceptor for a misactivated amino acid. GO:0002161 aminoacyl-tRNA deacylase activity and GO:0002196 Ser-tRNA(Ala) deacylase activity act on the charged tRNA, which ANKRD16 does not. GO:0140313 molecular sequestering activity, proposed by the Affinage record, does not fit either: the seryl group is covalently transferred to ANKRD16 lysines (the paper infers an amide adduct) and the adenylate is consumed, so this is a group transfer, not binding that withholds a molecule. GO:0008047 enzyme activator activity is too one-sided as a parent. ANKRD16 raises AlaRS serine-dependent ATP consumption but blocks transfer of serine to tRNA, so it regulates rather than activates the enzyme. Hence the parent GO:0030234 enzyme regulator activity. The three acceptor lysines are required, not just modified: mutating them abolishes the activity.
Parent term: enzyme regulator activity
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005634 nucleus | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Nucleus (IEA, from mouse ANKRD16 by the Ensembl ortholog pipeline). Mouse ANKRD16 is also detected in the nucleus; kept as non-core, since its known function is with cytoplasmic AlaRS. Reason: [PMID:29769718 "ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm"] No nuclear role has been described. Supporting Evidence: PMID:29769718 ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm |
| GO:0005634 nucleus | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Nucleus (ISS, from mouse ANKRD16 by sequence similarity). Mouse ANKRD16 is also detected in the nucleus; kept as non-core, since its known function is with cytoplasmic AlaRS. Reason: [PMID:29769718 "ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm"] No nuclear role has been described. Supporting Evidence: PMID:29769718 ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: Cytoplasm (IEA, from mouse ANKRD16 by the Ensembl ortholog pipeline). Mouse ANKRD16 is cytoplasmic in brain, where its partner AlaRS acts; accepted. Reason: [PMID:29769718 "ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm"] The transfer to human is reasonable for orthologs this close [file:human/ANKRD16/ANKRD16-bioinformatics/RESULTS.md "The two proteins are the same length and 82% identical."] Supporting Evidence: PMID:29769718 ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm file:human/ANKRD16/ANKRD16-bioinformatics/RESULTS.md The two proteins are the same length and 82% identical. |
| GO:0005737 cytoplasm | ISS GO_REF:0000024 | ACCEPT | Summary: Cytoplasm (ISS, from mouse ANKRD16 by sequence similarity). Mouse ANKRD16 is cytoplasmic in brain, where its partner AlaRS acts; accepted. Reason: [PMID:29769718 "ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm"] The transfer to human is reasonable for orthologs this close [file:human/ANKRD16/ANKRD16-bioinformatics/RESULTS.md "The two proteins are the same length and 82% identical."] Supporting Evidence: PMID:29769718 ANKRD16 was widely expressed in the brain and was detected in the nucleus as well as the cytoplasm file:human/ANKRD16/ANKRD16-bioinformatics/RESULTS.md The two proteins are the same length and 82% identical. |
| GO:0006400 tRNA modification | IEA GO_REF:0000107 | MODIFY | Summary: tRNA modification (IEA, from the mouse IDA). ANKRD16 does not alter tRNA nucleotides; it prevents serine from reaching tRNA(Ala) by accepting misactivated serine from AlaRS. The process is translational-fidelity editing of aminoacyl-tRNA formation. Reason: GO:0006400 is the covalent alteration of tRNA nucleotides. ANKRD16 instead acts at the aminoacylation step [PMID:29769718 "Serine that is misactivated by AlaRS is captured by the lysine side chains of ANKRD16, which prevents the charging of serine adenylates to tRNAAla and precludes serine misincorporation in nascent peptides."] [PMID:29769718 "Thus, ANKRD16 acts prior to formation of mischarged tRNA to enhance translational fidelity."] It does not act on the charged tRNA [PMID:29769718 "ANKRD16 had no effect on subsequent steps of tRNA mischarging including deacylation of mischarged Ser-tRNAAla"] GO:0106074 aminoacyl-tRNA metabolism involved in translational fidelity covers processes that keep tRNAs charged with the correct amino acid, and ANKRD16 does part of that work itself [PMID:29769718 "These results suggest that ANKRD16 functions as an alternative to water or tRNAAla, accepting misactivated serine."]. UniProt's function text says ANKRD16 promotes [file:human/ANKRD16/ANKRD16-uniprot.txt "tRNA(Ala) by promoting the hydrolysis of Ser-mischarged tRNA(Ala),"], but the paper found no effect of ANKRD16 on that step. The hydrolysis it stimulates is of ATP, before charging: [PMID:29769718 "ANKRD16 binds to AlaRS and prevents misincorporation of serine at alanine codons in nascent peptides by stimulating serine-dependent ATP hydrolysis prior to tRNA aminoacylation via acceptance of misactivated serines."] All six human rows are regenerated from the mouse A2AS55 annotations, so the lasting fix is to the mouse GO:0006400 IDA (PMID:29769718) and the UniProt function text. Proposed replacements: aminoacyl-tRNA metabolism involved in translational fidelity Supporting Evidence: PMID:29769718 Serine that is misactivated by AlaRS is captured by the lysine side chains of ANKRD16, which prevents the charging of serine adenylates to tRNAAla and precludes serine misincorporation in nascent peptides. PMID:29769718 Thus, ANKRD16 acts prior to formation of mischarged tRNA to enhance translational fidelity. PMID:29769718 ANKRD16 had no effect on subsequent steps of tRNA mischarging including deacylation of mischarged Ser-tRNAAla PMID:29769718 These results suggest that ANKRD16 functions as an alternative to water or tRNAAla, accepting misactivated serine. file:human/ANKRD16/ANKRD16-uniprot.txt tRNA(Ala) by promoting the hydrolysis of Ser-mischarged tRNA(Ala), PMID:29769718 ANKRD16 binds to AlaRS and prevents misincorporation of serine at alanine codons in nascent peptides by stimulating serine-dependent ATP hydrolysis prior to tRNA aminoacylation via acceptance of misactivated serines. |
| GO:0006400 tRNA modification | ISS GO_REF:0000024 | MODIFY | Summary: tRNA modification (ISS, from the mouse IDA). ANKRD16 does not alter tRNA nucleotides; it prevents serine from reaching tRNA(Ala) by accepting misactivated serine from AlaRS. The process is translational-fidelity editing of aminoacyl-tRNA formation. Reason: GO:0006400 is the covalent alteration of tRNA nucleotides. ANKRD16 instead acts at the aminoacylation step [PMID:29769718 "Serine that is misactivated by AlaRS is captured by the lysine side chains of ANKRD16, which prevents the charging of serine adenylates to tRNAAla and precludes serine misincorporation in nascent peptides."] [PMID:29769718 "Thus, ANKRD16 acts prior to formation of mischarged tRNA to enhance translational fidelity."] It does not act on the charged tRNA [PMID:29769718 "ANKRD16 had no effect on subsequent steps of tRNA mischarging including deacylation of mischarged Ser-tRNAAla"] GO:0106074 aminoacyl-tRNA metabolism involved in translational fidelity covers processes that keep tRNAs charged with the correct amino acid, and ANKRD16 does part of that work itself [PMID:29769718 "These results suggest that ANKRD16 functions as an alternative to water or tRNAAla, accepting misactivated serine."]. UniProt's function text says ANKRD16 promotes [file:human/ANKRD16/ANKRD16-uniprot.txt "tRNA(Ala) by promoting the hydrolysis of Ser-mischarged tRNA(Ala),"], but the paper found no effect of ANKRD16 on that step. The hydrolysis it stimulates is of ATP, before charging: [PMID:29769718 "ANKRD16 binds to AlaRS and prevents misincorporation of serine at alanine codons in nascent peptides by stimulating serine-dependent ATP hydrolysis prior to tRNA aminoacylation via acceptance of misactivated serines."] All six human rows are regenerated from the mouse A2AS55 annotations, so the lasting fix is to the mouse GO:0006400 IDA (PMID:29769718) and the UniProt function text. Proposed replacements: aminoacyl-tRNA metabolism involved in translational fidelity Supporting Evidence: PMID:29769718 Serine that is misactivated by AlaRS is captured by the lysine side chains of ANKRD16, which prevents the charging of serine adenylates to tRNAAla and precludes serine misincorporation in nascent peptides. PMID:29769718 Thus, ANKRD16 acts prior to formation of mischarged tRNA to enhance translational fidelity. PMID:29769718 ANKRD16 had no effect on subsequent steps of tRNA mischarging including deacylation of mischarged Ser-tRNAAla PMID:29769718 These results suggest that ANKRD16 functions as an alternative to water or tRNAAla, accepting misactivated serine. file:human/ANKRD16/ANKRD16-uniprot.txt tRNA(Ala) by promoting the hydrolysis of Ser-mischarged tRNA(Ala), PMID:29769718 ANKRD16 binds to AlaRS and prevents misincorporation of serine at alanine codons in nascent peptides by stimulating serine-dependent ATP hydrolysis prior to tRNA aminoacylation via acceptance of misactivated serines. |
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Download this section (compressed HTML)Q: Does human ANKRD16 capture misactivated serine from human AlaRS (AARS1), and are ANKRD16 levels relevant to AARS1 editing-domain variants in human neurological disease?
Q: Does ANKRD16 have a role in the nucleus, where it is also detected?
Q: Should the mouse ANKRD16 GO:0006400 tRNA modification IDA (PMID:29769718), the source of every human row, be revised to GO:0106074, and the UniProt function text corrected to drop Ser-tRNA(Ala) hydrolysis?
Experiment: Reconstitute human AARS1 with human ANKRD16 (wild type and K102R/K135R/K165R) and measure serine-dependent ATP hydrolysis and Ser-tRNA(Ala) formation, to confirm the mouse mechanism in the human proteins.
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