9QAX: Telomerase reverse transcriptase

The catalytic core with C2 symmetry of human telomerase dimer. Determined by electron microscopy at 3.3 Å resolution. Released 16 Jul 2025.

Method: Electron microscopy
Resolution: 3.3 Å
Organism: Homo sapiens
Chains: 6
Atoms: 15,471
Mol. weight: 378.06 kDa
Released: 16 Jul 2025

Explore 9QAX in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9QAX contains 64 α-helices and 50 β-strands across 4 chains. Residue ranges use author residue numbering, as in the PDB file, from PDBe. To see them in 3D, choose the Cartoon representation with Secondary structure coloring: helices, sheets and coils get different colors.

Chain A: 52 helices, 39 β-strands

Element	Residues	Length	Sheet
α-helix	8-14	7
α-helix	15-17	3
β-strand	21-23	3	1
α-helix	24-31	8
α-helix	33	1
α-helix	45-53	9
β-strand	54-57	4	1
α-helix	77-91	15
β-strand	101-103	3	2
β-strand	119-121	3	2
α-helix	126-132	7
α-helix	135-144	10
α-helix	146-154	9
β-strand	157-162	6	1
β-strand	166-169	4	1
β-strand	325-327	3	3
α-helix	328-331	4
β-strand	332	1	4
α-helix	341-342	2
α-helix	346-349	4
α-helix	354-365	12
α-helix	378-383	6
α-helix	384-387	4
α-helix	390-401	12
α-helix	405-412	8
α-helix	445-453	9
β-strand	456	1	4
α-helix	458-472	15
α-helix	475-478	4
α-helix	481-496	16
β-strand	502-504	3	3
α-helix	505-508	4
α-helix	518-520	3
α-helix	531-547	17
α-helix	548-553	6
α-helix	554-560	7
β-strand	561-564	4	4
β-strand	574-577	4	4
α-helix	578-596	19
α-helix	598	1
β-strand	599-600	2	5
α-helix	601	1
α-helix	603-611	9
α-helix	615-616	2
β-strand	617-626	10	5
β-strand	629-636	8	5
α-helix	654-671	18
α-helix	673-675	3
β-strand	679-680	2	6
α-helix	683-697	15
α-helix	703-704	2
β-strand	709-712	4	6
β-strand	713	1	7
α-helix	722-733	12
β-strand	738-739	2	8
β-strand	740-749	10	1
β-strand	755-764	10	1
α-helix	766-768	3
α-helix	773-783	11
β-strand	789-796	8	1
β-strand	800-801	2	8
α-helix	802-813	12
β-strand	816-820	5	5
β-strand	823-826	4	5
α-helix	838-853	16
α-helix	855-858	4
β-strand	862-866	5	6
β-strand	869-873	5	6
α-helix	877-889	13
β-strand	891	1	9
β-strand	896	1	9
β-strand	898	1	7
β-strand	904-905	2	6
β-strand	920-921	2	6
β-strand	927-930	4	10
β-strand	933-936	4	10
β-strand	942-944	3	10
α-helix	947-949	3
β-strand	953	1	11
α-helix	966-981	16
α-helix	984-987	4
α-helix	994-1016	23
α-helix	1025-1027	3
α-helix	1030-1050	21
β-strand	1058	1	12
β-strand	1062	1	12
α-helix	1067-1084	18
α-helix	1086-1106	21
α-helix	1110-1118	9
α-helix	1125-1128	4
β-strand	1131	1	11

Chain L: 4 helices, 0 β-strands

Element	Residues	Length
α-helix	31-37	7
α-helix	47-72	26
α-helix	81-90	10
α-helix	92-98	7

Chain M: 4 helices, 0 β-strands

Element	Residues	Length
α-helix	41-49	9
α-helix	57-85	29
α-helix	96-102	7
α-helix	108-124	17

Chain O: 4 helices, 11 β-strands

Element	Residues	Length	Sheet
α-helix	99-103	5
β-strand	113-122	10	13
β-strand	142-147	6	13
β-strand	152-157	6	13
α-helix	159-163	5
β-strand	180	1	14
β-strand	181-184	4	13
β-strand	186	1	15
β-strand	189-190	2	13
β-strand	203-206	4	13
β-strand	208	1	15
β-strand	215	1	14
α-helix	217-220	4
β-strand	223	1	13
α-helix	228-237	10

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Telomerase reverse transcriptase	A	protein	1332	Homo sapiens	O14746 (AlphaFold model)
hTR, human telomerase RNA	B	RNA	451	Homo sapiens
Histone H2A	L	protein	130	Homo sapiens	B2R5B3 (AlphaFold model)
Histone H2B	M	protein	166	Homo sapiens	B4DR52 (AlphaFold model)
DNA (5'-d(pgptptpapgpgp*g)-3')	N	DNA	7	Homo sapiens
Adrenocortical dysplasia protein homolog	O	protein	458	Homo sapiens	Q96AP0 (AlphaFold model)

Sequence of entity 1 (A), FASTA

>9QAX_1 Telomerase reverse transcriptase (chains A)
MKTAALAQHDEAVDNKFNKEQQNAFYEILHLPNLNEEQRNAFIQSLKDDPSQSANLLAEA
KKLNDAQAPKVDNKFNKEQQNAFYEILHLPNLNEEQRNAFIQSLKDDPSQSANLLAEAKK
LNGAQAPKVDANSAGKSTDYDIPTTASENLYFQGHKLGTFQGPWSHPQFEKGSAGSAAGS
GAGWSHPQFEKSRPTTASGTMPRAPRCRAVRSLLRSHYREVLPLATFVRRLGPQGWRLVQ
RGDPAAFRALVAQCLVCVPWDARPPPAAPSFRQVSCLKELVARVLQRLCERGAKNVLAFG
FALLDGARGGPPEAFTTSVRSYLPNTVTDALRGSGAWGLLLRRVGDDVLVHLLARCALFV
LVAPSCAYQVCGPPLYQLGAATQARPPPHASGPRRRLGCERAWNHSVREAGVPLGLPAPG
ARRRGGSASRSLPLPKRPRRGAAPEPERTPVGQGSWAHPGRTRGPSDRGFCVVSPARPAE
EATSLEGALSGTRHSHPSVGRQHHAGPPSTSRPPRPWDTPCPPVYAETKHFLYSSGDKEQ
LRPSFLLSSLRPSLTGARRLVETIFLGSRPWMPGTPRRLPRLPQRYWQMRPLFLELLGNH
AQCPYGVLLKTHCPLRAAVTPAAGVCAREKPQGSVAAPEEEDTDPRRLVQLLRQHSSPWQ
VYGFVRACLRRLVPPGLWGSRHNERRFLRNTKKFISLGKHAKLSLQELTWKMSVRDCAWL
RRSPGVGCVPAAEHRLREEILAKFLHWLMSVYVVELLRSFFYVTETTFQKNRLFFYRKSV
WSKLQSIGIRQHLKRVQLRELSEAEVRQHREARPALLTSRLRFIPKPDGLRPIVNMDYVV
GARTFRREKRAERLTSRVKALFSVLNYERARRPGLLGASVLGLDDIHRAWRTFVLRVRAQ
DPPPELYFVKVDVTGAYDTIPQDRLTEVIASIIKPQNTYCVRRYAVVQKAAHGHVRKAFK
SHVSTLTDLQPYMRQFVAHLQETSPLRDAVVIEQSSSLNEASSGLFDVFLRFMCHHAVRI
RGKSYVQCQGIPQGSILSTLLCSLCYGDMENKLFAGIRRDGLLLRLVDDFLLVTPHLTHA
KTFLRTLVRGVPEYGCVVNLRKTVVNFPVEDEALGGTAFVQMPAHGLFPWCGLLLDTRTL
EVQSDYSSYARTSIRASLTFNRGFKAGRNMRRKLFGVLRLKCHSLFLDLQVNSLQTVCTN
IYKILLLQAYRFHACVLQLPFHQQVWKNPTFFLRVISDTASLCYSILKAKNAGMSLGAKG
AAGPLPSEAVQWLCHQAFLLKLTRHRVTYVPLLGSLRTAQTQLSRKLPGTTLTALEAAAN
PALPSDFKTILD

Sequence of entity 2 (B), FASTA

>9QAX_2 hTR, human telomerase RNA (chains B)
GGGUUGCGGAGGGUGGGCCUGGGAGGGGUGGUGGCCAUUUUUUGUCUAACCCUAACUGAG
AAGGGCGUAGGCGCCGUGCUUUUGCUCCCCGCGCGCUGUUUUUCUCGCUGACUUUCAGCG
GGCGGAAAAGCCUCGGCCUGCCGCCUUCCACCGUUCAUUCUAGAGCAAACAAAAAAUGUC
AGCUGCUGGCCCGUUCGCCCCUCCCGGGGACCUGCGGCGGGUCGCCUGCCCAGCCCCCGA
ACCCCGCCUGGAGGCCGCGGUCGGCCCGGGGCUUCUCCGGAGGCACCCACUGCCACCGCG
AAGAGUUGGGCUCUGUCAGCCGCGGGUCUCUCGGGGGCGAGGGCGAGGUUCAGGCCUUUC
AGGCCGCAGGAAGAGGAACGGAGCGAGUCCCCGCGCGCGGCGCGAUUCCCUGAGCUGUGG
GACGUGCACCCAGGACUCGGCUCACACAUGC

Sequence of entity 3 (L), FASTA

>9QAX_3 Histone H2A (chains L)
MSGRGKQGGKARAKAKTRSSRAGLQFPVGRVRRLLRKGNYAERVGAGAPVYLAAVLEYLT
AEILELAGNAARDNKKTRIIPRHLQLAIRNDEELNKLLGKVTIAQGGVLPNIQAVLLPKK
TESHHKAKGK

Sequence of entity 4 (M), FASTA

>9QAX_4 Histone H2B (chains M)
MPDPAKSAPAPKKGSKKAVTKVQKKDGKKRKRSRKESYSVYVYKVLKQVHPDTGISSKAM
GIMNSFVNDIFERIAGEASRLAHYNKRSTITSREIQTAVRLLLPGELAKHAVSEGTKAVT
KYTSSNPRNLSPTKPGGSEDRQPPPSQLSAIPPFCLVLRAGIAGQV

Sequence of entity 5 (N), FASTA

>9QAX_5 DNA (5'-D(P*GP*TP*TP*AP*GP*GP*G)-3') (chains N)
GTTAGGG

Sequence of entity 6 (O), FASTA

>9QAX_6 Adrenocortical dysplasia protein homolog (chains O)
MAGSGRLVLRPWIRELILGSETPSSPRAGQLLEVLQDAEAAVAGPSHAPDTSDVGATLLV
SDGTHSVRCLVTREALDTSDWEEKEFGFRGTEGRLLLLQDCGVHVQVAEGGAPAEFYLQV
DRFSLLPTEQPRLRVPGCNQDLDVQKKLYDCLEEHLSESTSSNAGLSLSQLLDEMREDQE
HQGALVCLAESCLTLEGPCTAPPVTHWAASRCKATGEAVYTVPSSMLCISENDQLILSSL
GPCQRTQGPELPPPDPALQDLSLTLIASPPSSPSSSGTPALPGHMSSEESGTSISLLPAL
SLAAPDPGQRSSSQPSPAICSAPATLTPRSPHASRTPSSPLQSCTPSLSPRSHVPSPHQA
LVTRPQKPSLEFKEFVGLPCKNRPPFPRTGATRGAQEPCSVWEPPKRHRDGSAFQYEYEP
PCTSLCARVQAVRLPPQLMAWALHFLMDAQPGSEPTPM

Primary citation

Cryo-EM structure of human telomerase dimer reveals H/ACA RNP-mediated dimerization. Balch, S., Sekne, Z., Franco-Echevarria, E. et al. Science (2025) 389:eadr5817-eadr5817. DOI 10.1126/science.adr5817 · PubMed

Other PDB entries of the same protein (UniProt O14746 (AlphaFold model), which also has an AlphaFold model), best resolution first:

5MEO 1.77 Å, Human Leukocyte Antigen presenting ILGKFLHRL
5MER 1.88 Å, Human Leukocyte Antigen A02 presenting ILAKFLHEL
5MEQ 2.27 Å, Human Leukocyte Antigen A02 presenting ILAKFLHTL
5UGW 2.31 Å, Structure of the human telomerase thumb domain
4B18 2.52 Å, The crystal structure of human Importin alpha 5 with TERT NLS peptide
9Q16 2.7 Å, Human telomerase catalytic core with shelterin protein TPP1, dGpNHpp and DNA primer…
5MEP 2.71 Å, Human Leukocyte Antigen A02 presenting ILGKFLHWL
4MNQ 2.74 Å, TCR-peptide specificity overrides affinity enhancing TCR-MHC interactions
2BCK 2.8 Å, Crystal Structure of HLA-A*2402 Complexed with a telomerase peptide
9Q12 2.8 Å, Human telomerase catalytic core with shelterin protein TPP1 and DNA primer ending in TTAG
5MEN 2.81 Å, Human Leukocyte Antigen A02 presenting ILAKFLHWL, in complex with cognate T-Cell Receptor
9Q10 2.9 Å, Human telomerase catalytic core with shelterin protein TPP1, dTpNHpp and DNA primer…

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