9SI0: Histone H2A

Cryo-EM structure of the catalytic core of human telomerase at the pre-termination state of the repeat addition cycle. Determined by electron microscopy at 3.8 Å resolution. Released 28 Jan 2026.

Method: Electron microscopy
Resolution: 3.8 Å
Organism: Homo sapiens
Chains: 6
Atoms: 15,563
Mol. weight: 364.83 kDa
Ligands: 1GC
Released: 28 Jan 2026

Explore 9SI0 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9SI0 contains 70 α-helices and 42 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: 57 helices, 34 β-strands

Element	Residues	Length	Sheet
α-helix	8-17	10
β-strand	20-23	4	3
α-helix	24-31	8
α-helix	33	1
α-helix	36-40	5
α-helix	45-53	9
β-strand	54-58	5	3
α-helix	77-91	15
α-helix	96-98	3
β-strand	101-103	3	4
β-strand	119-121	3	4
α-helix	126-132	7
α-helix	135-144	10
α-helix	146-154	9
β-strand	157-161	5	3
β-strand	167-169	3	3
β-strand	325-327	3	5
α-helix	340-342	3
α-helix	346-349	4
α-helix	354-366	13
α-helix	380-383	4
α-helix	384-387	4
α-helix	390-402	13
α-helix	405-412	8
α-helix	445-451	7
β-strand	456	1	6
α-helix	458-472	15
α-helix	481-494	14
β-strand	502-504	3	5
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	561-565	5	6
β-strand	573-577	5	6
α-helix	578-595	18
β-strand	599-600	2	7
α-helix	601-602	2
α-helix	603-611	9
α-helix	615-617	3
β-strand	618-625	8	7
β-strand	630-636	7	7
α-helix	637-639	3
α-helix	649-651	3
α-helix	654-656	3
α-helix	657-671	15
α-helix	673-676	4
β-strand	679	1	8
α-helix	683-699	17
α-helix	703-705	3
β-strand	707-711	5	8
α-helix	712	1
β-strand	713	1	9
α-helix	722-732	11
β-strand	739-748	10	3
β-strand	756-764	9	3
α-helix	766-768	3
α-helix	773-783	11
β-strand	789-800	12	3
α-helix	802-810	9
α-helix	811-815	5
β-strand	817-820	4	7
β-strand	823-826	4	7
α-helix	836-854	19
α-helix	857-859	3
β-strand	863-865	3	8
β-strand	870-874	5	8
α-helix	877-889	13
β-strand	891	1	10
β-strand	896	1	10
β-strand	898	1	9
α-helix	900-902	3
β-strand	904-905	2	8
β-strand	920-921	2	8
β-strand	927-930	4	11
β-strand	933-936	4	11
β-strand	942-944	3	11
α-helix	947-949	3
β-strand	953	1	12
α-helix	954-957	4
α-helix	966-981	16
α-helix	984-987	4
α-helix	994-1016	23
α-helix	1025-1027	3
α-helix	1029-1050	22
α-helix	1067-1083	17
α-helix	1086-1106	21
α-helix	1109-1117	9
α-helix	1125-1128	4
β-strand	1131	1	12

Chain L: 4 helices, 1 β-strand

Element	Residues	Length	Sheet
α-helix	31-37	7
α-helix	47-73	27
β-strand	79	1	1
α-helix	81-90	10
α-helix	92-98	7

Chain M: 4 helices, 1 β-strand

Element	Residues	Length	Sheet
α-helix	39-49	11
β-strand	55	1	1
α-helix	57-85	29
α-helix	92-102	11
α-helix	105-124	20

Chain O: 5 helices, 6 β-strands

Element	Residues	Length	Sheet
α-helix	98-103	6
β-strand	113-123	11	2
β-strand	142-147	6	2
β-strand	152-157	6	2
α-helix	159-164	6
α-helix	170-172	3
β-strand	180-190	11	2
β-strand	203-215	13	2
α-helix	217-220	4
β-strand	223	1	2
α-helix	228-237	10

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Histone H2A	L	protein	130	Homo sapiens	B2R5B3 (AlphaFold model)
Histone H2B	M	protein	166	Homo sapiens	B4DR52 (AlphaFold model)
DNA (5'-d(pgptptpapgpgpgptptpa)-3')	N	DNA	33	Homo sapiens
Adrenocortical dysplasia protein homolog	O	protein	458	Homo sapiens	Q96AP0 (AlphaFold model)
hTR, human telomerase RNA	B	RNA	451	Homo sapiens
Telomerase reverse transcriptase	A	protein	1132	Homo sapiens	O14746 (AlphaFold model)

Sequence of entity 1 (L), FASTA

>9SI0_1 Histone H2A (chains L)
MSGRGKQGGKARAKAKTRSSRAGLQFPVGRVRRLLRKGNYAERVGAGAPVYLAAVLEYLT
AEILELAGNAARDNKKTRIIPRHLQLAIRNDEELNKLLGKVTIAQGGVLPNIQAVLLPKK
TESHHKAKGK

Sequence of entity 2 (M), FASTA

>9SI0_2 Histone H2B (chains M)
MPDPAKSAPAPKKGSKKAVTKVQKKDGKKRKRSRKESYSVYVYKVLKQVHPDTGISSKAM
GIMNSFVNDIFERIAGEASRLAHYNKRSTITSREIQTAVRLLLPGELAKHAVSEGTKAVT
KYTSSNPRNLSPTKPGGSEDRQPPPSQLSAIPPFCLVLRAGIAGQV

Sequence of entity 3 (N), FASTA

>9SI0_3 DNA (5'-D(P*GP*TP*TP*AP*GP*GP*GP*TP*TP*A)-3') (chains N)
TTAGGGTTAGGGTTAGGGTTAGGGTTAGGGTTA

Sequence of entity 4 (O), FASTA

>9SI0_4 Adrenocortical dysplasia protein homolog (chains O)
MAGSGRLVLRPWIRELILGSETPSSPRAGQLLEVLQDAEAAVAGPSHAPDTSDVGATLLV
SDGTHSVRCLVTREALDTSDWEEKEFGFRGTEGRLLLLQDCGVHVQVAEGGAPAEFYLQV
DRFSLLPTEQPRLRVPGCNQDLDVQKKLYDCLEEHLSESTSSNAGLSLSQLLDEMREDQE
HQGALVCLAESCLTLEGPCTAPPVTHWAASRCKATGEAVYTVPSSMLCISENDQLILSSL
GPCQRTQGPELPPPDPALQDLSLTLIASPPSSPSSSGTPALPGHMSSEESGTSISLLPAL
SLAAPDPGQRSSSQPSPAICSAPATLTPRSPHASRTPSSPLQSCTPSLSPRSHVPSPHQA
LVTRPQKPSLEFKEFVGLPCKNRPPFPRTGATRGAQEPCSVWEPPKRHRDGSAFQYEYEP
PCTSLCARVQAVRLPPQLMAWALHFLMDAQPGSEPTPM

Sequence of entity 5 (B), FASTA

>9SI0_5 hTR, human telomerase RNA (chains B)
GGGUUGCGGAGGGUGGGCCUGGGAGGGGUGGUGGCCAUUUUUUGUCUAACCCUAACUGAG
AAGGGCGUAGGCGCCGUGCUUUUGCUCCCCGCGCGCUGUUUUUCUCGCUGACUUUCAGCG
GGCGGAAAAGCCUCGGCCUGCCGCCUUCCACCGUUCAUUCUAGAGCAAACAAAAAAUGUC
AGCUGCUGGCCCGUUCGCCCCUCCCGGGGACCUGCGGCGGGUCGCCUGCCCAGCCCCCGA
ACCCCGCCUGGAGGCCGCGGUCGGCCCGGGGCUUCUCCGGAGGCACCCACUGCCACCGCG
AAGAGUUGGGCUCUGUCAGCCGCGGGUCUCUCGGGGGCGAGGGCGAGGUUCAGGCCUUUC
AGGCCGCAGGAAGAGGAACGGAGCGAGUCCCCGCGCGCGGCGCGAUUCCCUGAGCUGUGG
GACGUGCACCCAGGACUCGGCUCACACAUGC

Sequence of entity 6 (A), FASTA

>9SI0_6 Telomerase reverse transcriptase (chains A)
MPRAPRCRAVRSLLRSHYREVLPLATFVRRLGPQGWRLVQRGDPAAFRALVAQCLVCVPW
DARPPPAAPSFRQVSCLKELVARVLQRLCERGAKNVLAFGFALLDGARGGPPEAFTTSVR
SYLPNTVTDALRGSGAWGLLLRRVGDDVLVHLLARCALFVLVAPSCAYQVCGPPLYQLGA
ATQARPPPHASGPRRRLGCERAWNHSVREAGVPLGLPAPGARRRGGSASRSLPLPKRPRR
GAAPEPERTPVGQGSWAHPGRTRGPSDRGFCVVSPARPAEEATSLEGALSGTRHSHPSVG
RQHHAGPPSTSRPPRPWDTPCPPVYAETKHFLYSSGDKEQLRPSFLLSSLRPSLTGARRL
VETIFLGSRPWMPGTPRRLPRLPQRYWQMRPLFLELLGNHAQCPYGVLLKTHCPLRAAVT
PAAGVCAREKPQGSVAAPEEEDTDPRRLVQLLRQHSSPWQVYGFVRACLRRLVPPGLWGS
RHNERRFLRNTKKFISLGKHAKLSLQELTWKMSVRDCAWLRRSPGVGCVPAAEHRLREEI
LAKFLHWLMSVYVVELLRSFFYVTETTFQKNRLFFYRKSVWSKLQSIGIRQHLKRVQLRE
LSEAEVRQHREARPALLTSRLRFIPKPDGLRPIVNMDYVVGARTFRREKRAERLTSRVKA
LFSVLNYERARRPGLLGASVLGLDDIHRAWRTFVLRVRAQDPPPELYFVKVDVTGAYDTI
PQDRLTEVIASIIKPQNTYCVRRYAVVQKAAHGHVRKAFKSHVSTLTDLQPYMRQFVAHL
QETSPLRDAVVIEQSSSLNEASSGLFDVFLRFMCHHAVRIRGKSYVQCQGIPQGSILSTL
LCSLCYGDMENKLFAGIRRDGLLLRLVDDFLLVTPHLTHAKTFLRTLVRGVPEYGCVVNL
RKTVVNFPVEDEALGGTAFVQMPAHGLFPWCGLLLDTRTLEVQSDYSSYARTSIRASLTF
NRGFKAGRNMRRKLFGVLRLKCHSLFLDLQVNSLQTVCTNIYKILLLQAYRFHACVLQLP
FHQQVWKNPTFFLRVISDTASLCYSILKAKNAGMSLGAKGAAGPLPSEAVQWLCHQAFLL
KLTRHRVTYVPLLGSLRTAQTQLSRKLPGTTLTALEAAANPALPSDFKTILD

Ligands and cofactors

ID	Name	Formula	Copies
1GC	2'-deoxy-5'-O-[(R)-hydroxy{[(S)-hydroxy(phosphonooxy)phosphoryl]methyl}phosphor…	C11 H18 N5 O12 P3	1

Primary citation

Structures of nucleotide-bound human telomerase at several steps of its telomeric DNA repeat addition cycle. Balch, S., Franco-Echevarria, E., Ghanim, G.E. et al. Nat Commun (2026) 17:1847-1847. DOI 10.1038/s41467-026-68560-8 · PubMed

Other PDB entries of the same protein (UniProt B2R5B3 (AlphaFold model), which also has an AlphaFold model), best resolution first:

7QXA 3.2 Å, Cryo-EM map of human telomerase-DNA-TPP1 complex (sharpened)
9SHZ 3.2 Å, Cryo-EM structure of the catalytic core of human telomerase at the elongation state of…
9QAX 3.3 Å, The catalytic core with C2 symmetry of human telomerase dimer
9SHY 3.53 Å, Cryo-EM structure of the catalytic core of human telomerase at the initiation state of…
9QAZ 3.6 Å, Catalytic core 2 of dimeric human telomerase
9QAY 3.8 Å, Catalytic core 1 of dimeric human telomerase
7QXB 3.9 Å, Cryo-EM map of human telomerase-DNA-TPP1-POT1 complex (sharpened map)
7QXS 3.9 Å, Cryo-EM structure of human telomerase-DNA-TPP1-POT1 complex (with POT1 side chains)

Browse structure collections

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