9RYC: Human 1918 influenza A polymerase heterotrimer

Structure of human 1918 influenza A polymerase heterotrimer in complex with WSN NEP. Determined by electron microscopy at 2.93 Å resolution. Released 24 Dec 2025.

Method: Electron microscopy
Resolution: 2.93 Å
Organism: Influenza A virus (A/Brevig Mission/1/1918(H1N1))
Chains: 4
Atoms: 14,502
Mol. weight: 271.4 kDa
Released: 24 Dec 2025

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

Secondary structure: helices and β-sheets

9RYC contains 87 α-helices and 69 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: 33 helices, 28 β-strands

Element	Residues	Length	Sheet
α-helix	2-7	6
α-helix	11-24	14
α-helix	32-48	17
β-strand	53-54	2	1
β-strand	60-61	2	1
β-strand	73	1	1
β-strand	76-78	3	2
α-helix	84-98	15
β-strand	109-111	3	2
β-strand	116-123	8	2
α-helix	127-137	11
β-strand	143-149	7	2
β-strand	154-156	3	2
α-helix	157-159	3
α-helix	165-185	21
α-helix	190-193	4
α-helix	212-215	4
α-helix	226-234	9
α-helix	241-248	8
β-strand	258-259	2	3
β-strand	275	1	4
α-helix	276	1
β-strand	287	1	5
β-strand	290-292	3	5
α-helix	303-312	10
β-strand	317-324	8	5
α-helix	331-348	18
β-strand	359-360	2	6
α-helix	361	1
α-helix	364-369	6
α-helix	375-376	2
β-strand	377-378	2	7
α-helix	381-384	4
β-strand	391-392	2	7
α-helix	397-400	4
β-strand	402	1	4
α-helix	406-414	9
β-strand	417	1	8
α-helix	425-427	3
α-helix	429-431	3
α-helix	434-450	17
β-strand	453	1	8
α-helix	454-475	22
β-strand	480-481	2	6
β-strand	482-491	10	5
β-strand	494-506	13	5
α-helix	516-517	2
β-strand	518-526	9	5
α-helix	534-537	4
β-strand	541-551	11	5
β-strand	556-570	15	5
α-helix	572-579	8
α-helix	583-601	19
α-helix	602-604	3
β-strand	619-623	5	9
β-strand	628-631	4	9
α-helix	633-649	17
α-helix	653-673	21
β-strand	679-680	2	3
α-helix	683-691	9
α-helix	698-714	17

Chain B: 34 helices, 26 β-strands

Element	Residues	Length	Sheet
β-strand	2-3	2	9
α-helix	5-10	6
α-helix	18-21	4
α-helix	36-48	13
β-strand	54-57	4	10
β-strand	64-67	4	10
α-helix	72-74	3
α-helix	85-98	14
α-helix	102-115	14
α-helix	119-123	5
β-strand	128-130	3	11
β-strand	135-137	3	11
α-helix	139-152	14
α-helix	163-173	11
β-strand	178-181	4	12
β-strand	210-213	4	12
α-helix	214-221	8
β-strand	223-225	3	13
β-strand	243-244	2	13
α-helix	251-264	14
β-strand	269	1	3
α-helix	278-289	12
β-strand	298-303	6	3
β-strand	305	1	14
α-helix	310-312	3
α-helix	315-325	11
α-helix	331-337	7
α-helix	340-344	5
β-strand	348-350	3	13
β-strand	355-358	4	7
β-strand	364-368	5	7
α-helix	370-372	3
α-helix	378-380	3
α-helix	383-392	10
α-helix	393-395	3
β-strand	396-397	2	13
β-strand	400-402	3	13
α-helix	413-425	13
β-strand	437-442	6	3
β-strand	446	1	14
β-strand	447-453	7	3
α-helix	456-472	17
β-strand	483-486	4	3
β-strand	489-492	4	15
β-strand	495-498	4	15
β-strand	501-504	4	15
α-helix	508-511	4
α-helix	521-536	16
α-helix	541-559	19
α-helix	573-582	10
α-helix	591-593	3
α-helix	601-603	3
α-helix	608-612	5
α-helix	618-624	7
β-strand	667-668	2	16
α-helix	688-699	12
α-helix	701-704	4
β-strand	713	1	17
α-helix	714-732	19
α-helix	737-755	19

Chain C: 16 helices, 15 β-strands

Element	Residues	Length	Sheet
α-helix	2-12	11
α-helix	15-22	8
β-strand	24	1	17
α-helix	25-28	4
α-helix	31-33	3
α-helix	43-52	10
β-strand	57-58	2	16
α-helix	63-66	4
β-strand	70	1	18
β-strand	76	1	18
β-strand	78-79	2	16
β-strand	90-91	2	16
α-helix	93-102	10
α-helix	111-114	4
α-helix	116-126	11
β-strand	129-135	7	19
β-strand	141-148	8	20
α-helix	156-166	11
α-helix	169-171	3
α-helix	174-178	5
α-helix	184-192	9
α-helix	200-211	12
β-strand	214-220	7	20
β-strand	236	1	19
β-strand	240-245	6	19
β-strand	694-699	6	21
α-helix	702-704	3
β-strand	708	1	21
α-helix	713-715	3
β-strand	721-725	5	21
β-strand	731-736	6	21

Chain D: 4 helices, 0 β-strands

Element	Residues	Length
α-helix	9-21	13
α-helix	26-50	25
α-helix	62-89	28
α-helix	93-120	28

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Polymerase acidic protein	A	protein	716	Influenza A virus (A/Brevig Mission/1/1918(H1N1))	Q3HM39
RNA-directed RNA polymerase catalytic subunit	B	protein	757	Influenza A virus (A/Brevig Mission/1/1918(H1N1))	Q3HM40
Polymerase basic protein 2	C	protein	765	Influenza A virus (A/Brevig Mission/1/1918(H1N1))	Q3HM41
Nuclear export protein	D	protein	130	Influenza A virus (A/Brevig Mission/1/1918(H1N1))	Q77IX1

Sequence of entity 1 (A), FASTA

>9RYC_1 Polymerase acidic protein (chains A)
MEDFVRQCFNPMIVELAEKAMKEYGEDLKIETNKFAAICTHLEVCFMYSDFHFINERGES
IIVESGDPNALLKHRFEIIEGRDRTMAWTVVNSICNTTGAEKPKFLPDLYDYKENRFIEI
GVTRREVHIYYLEKANKIKSEKTHIHIFSFTGEEMATKADYTLDEESRARIKTRLFTIRQ
EMASRGLWDSFRQSERGEETIEERFEITGTMRRLADQSLPPNFSSLENFRAYVDGFEPNG
YIEGKLSQMSKEVNARIEPFLKTTPRPLRLPDGPPCSQRSKFLLMDALKLSIEDPSHEGE
GIPLYDAIKCMRTFFGWKEPNVVKPHEKGINPNYLLAWKQVLAELQDIENEEKIPKTKNM
KKTSQLKWALGENMAPEKVDFDDCKDVSDLKQYDSDEPELRSLASWIQSEFNKACELTDS
SWIELDEIGEDVAPIEHIASMRRNYFTAEVSHCRATEYIMKGVYINTALLNASCAAMDDF
QLIPMISKCRTKEGRRKTNLYGFIIKGRSHLRNDTDVVNFVSMEFSLTDPRLEPHKWEKY
CVLEIGDMLLRSAIGQVSRPMFLYVRTNGTSKIKMKWGMEMRRCLLQSLQQIESMIEAES
SVKEKDMTKEFFENKSETWPIGESPKGVEEGSIGKVCRTLLAKSVFNSLYASPQLEGFSA
ESRKLLLIVQALRDNLEPGTFDLGGLYEAIEECLINDPWVLLNASWFNSFLTHALR

Sequence of entity 2 (B), FASTA

>9RYC_2 RNA-directed RNA polymerase catalytic subunit (chains B)
MDVNPTLLFLKVPAQNAISTTFPYTGDPPYSHGTGTGYTMDTVNRTHQYSEKGRWTTNTE
TGAPQLNPIDGPLPEDNEPSGYAQTDCVLEAMAFLEESHPGIFENSCLETMEVVQQTRVD
KLTQGRQTYDWTLNRNQPAATALANTIEVFRSNGLTANESGRLIDFLKDVMESMDKEEME
ITTHFQRKRRVRDNMTKKMVTQRTIGKKKQRLNKRSYLIRALTLNTMTKDAERGKLKRRA
IATPGMQIRGFVYFVETLARSICEKLEQSGLPVGGNEKKAKLANVVRKMMTNSQDTELSF
TITGDNTKWNENQNPRMFLAMITYITRNQPEWFRNVLSIAPIMFSNKMARLGKGYMFESK
SMKLRTQIPAEMLASIDLKYFNDSTRKKIEKIRPLLIDGTASLSPGMMMGMFNMLSTVLG
VSILNLGQKRYTKTTYWWDGLQSSDDFALIVNAPNHEGIQAGVDRFYRTCKLLGINMSKK
KSYINRTGTFEFTSFFYRYGFVANFSMELPSFGVSGINESADMSIGVTVIKNNMINNDLG
PATAQMALQLFIKDYRYTYRCHRGDTQIQTRRSFEIKKLWEQTRSKAGLLVSDGGPNLYN
IRNLHIPEVCLKWELMDEDYQGRLCNPLNPFVSHKEIESVNNAVMMPAHGPAKNMEYDAV
ATTHSWIPKRNRSILNTSQRGILEDEQMYQKCCNLFEKFFPSSSYRRPVGISSMVEAMVS
RARIDARIDFESGRIKKEEFAEIMKICSTIEELRRQK

Sequence of entity 3 (C), FASTA

>9RYC_3 Polymerase basic protein 2 (chains C)
MERIKELRDLMSQSRTREILTKTTVDHMAIIKKYTSGRQEKNPALRMKWMMAMKYPITAD
KRIMEMIPERNEQGQTLWSKTNDAGSDRVMVSPLAVTWWNRNGPTTSAVHYPKIYKTYFE
KVERLKHGTFGPVHFRNQVKIRRRVDINPGHADLSAKEAQDVIMEVVFPNEVGARILTSE
SQLTITKEKKEELQDCKISPLMVAYMLERELVRKTRFLPVAGGTSSVYIEVLHLTQGTCW
EQMYTPGGEVRNDDVDQSLIIAARNIVRRATVSADPLASLLEMCHSTQIGGIRMVDILRQ
NPTEEQAVDICKAAMGLRISSSFSFGGFTFKRTSGSSVKREEEVLTGNLQTLKIRVHEGY
EEFTMVGRRATAILRKATRRLIQLIVSGRDEQSIAEAIIVAMVFSQEDCMIKAVRGDLNF
VNRANQRLNPMHQLLRHFQKDAKVLFQNWGIEPIDNVMGMIGILPDMTPSTEMSMRGVRV
SKMGVDEYSSTERVVVSIDRFLRVRDQRGNVLLSPEEVSETQGTEKLTITYSSSMMWEVN
GPESVLVNTYQWIIRNWETVKIQWSQNPTMLYNKMEFEPFQSLVPKAARGQYSGFVRTLF
QQMRDVLGTFDTVQIIKLLPFAAAPPKQSRMQFSSLTVNVRGSGMRILVRGNSPVFNYNK
ATKRLTVLGKDAGALTEDPDEGTAGVESAVLRGFLILGKEDRRYGPALSINELSNLAKGE
KANVLIGQGDVVLVMKRKRDSSILTDSQTATKRIRMAINENLYFQ

Sequence of entity 4 (D), FASTA

>9RYC_4 Nuclear export protein (chains D)
GPLGSPEFCMDSNTVSSFQDILMRMSKMQLGSSSEDLNGIITQFESLKLYRDSLGEAVMR
MGDLHSLQNRNGKWREQLGQKFEEIRWLIEEVRHRLKITENSFEQITFMQALQLLLEVEQ
EIRTFSFQLI

Primary citation

Regulatory hotspot on the influenza A virus polymerase revealed through the structure of the NEP-polymerase complex. Rep, A., Wang, F., Chen, K.Y. et al. Sci Adv (2026) 12:eaeb4073-eaeb4073. DOI 10.1126/sciadv.aeb4073 · PubMed

Other PDB entries of the same protein (UniProt Q3HM39), best resolution first:

9RVE 2.53 Å, Structure of human 1918 influenza A polymerase heterotrimer in complex with 1918 NEP.
7NHC 2.87 Å, 1918 H1N1 Viral influenza polymerase heterotrimer - Endonuclease ordered (Class2b)
7NHA 2.91 Å, 1918 H1N1 Viral influenza polymerase heterotrimer - Endonuclease and priming loop…
7NHX 3.23 Å, 1918 H1N1 Viral influenza polymerase heterotrimer - full transcriptase (Class1)
8R60 3.23 Å, 1918 H1N1 Viral polymerase heterotrimer in complex with 4 repeat serine-5 phosphorylated…
7NI0 3.32 Å, 1918 H1N1 Viral influenza polymerase heterotrimer - Replicase (class 3)
7NKA 4.07 Å, 1918 H1N1 Viral influenza polymerase heterotrimer with Nb8206
7NK1 4.22 Å, 1918 Influenza virus polymerase heterotirmer in complex with vRNA promoters and Nb8201
8R65 4.23 Å, 1918 H1N1 Viral polymerase heterotrimer in complex with 4 repeat serine-5 phosphorylated…
7NKC 4.46 Å, 1918 H1N1 Viral influenza polymerase heterotrimer with Nb8207
7NJ3 4.48 Å, 1918 H1N1 Viral influenza polymerase heterotrimer with Nb8196 core
7NJ5 4.63 Å, 1918 H1N1 Viral influenza polymerase heterotrimer with Nb8199 core

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