9N81: X-ray repair cross-complementing protein 6

A gap-filling complex with Pol mu engaged in the NHEJ Pathway. Determined by electron microscopy at 2.8 Å resolution. Released 23 Apr 2025.

Method: Electron microscopy
Resolution: 2.8 Å
Organism: Homo sapiens
Chains: 20
Atoms: 41,888
Mol. weight: 969.3 kDa
Ligands: DZ4, MG
Released: 23 Apr 2025

Explore 9N81 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9N81 contains 214 α-helices and 233 β-strands across 16 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: 20 helices, 28 β-strands

Element	Residues	Length	Sheet
β-strand	35-43	9	38
α-helix	46-49	4
α-helix	59-77	19
β-strand	82-88	7	38
β-strand	94	1	38
β-strand	102-109	8	38
α-helix	113-120	8
α-helix	125-134	10
α-helix	143-156	14
β-strand	161-169	9	38
α-helix	181-196	16
β-strand	199-202	4	38
β-strand	211	1	39
α-helix	217-220	4
α-helix	231	1
β-strand	232	1	39
α-helix	238-243	6
β-strand	257-262	6	40
β-strand	268-274	7	40
β-strand	277	1	41
α-helix	282-285	4
β-strand	286-289	4	42
β-strand	295	1	42
β-strand	296-304	9	43
β-strand	310	1	43
β-strand	317-321	5	44
β-strand	326-329	4	44
α-helix	331-336	6
β-strand	344-352	9	40
α-helix	358-360	3
β-strand	366-370	5	40
β-strand	375-376	2	45
α-helix	378-392	15
β-strand	394-401	8	40
β-strand	409-416	8	40
β-strand	419-420	2	46
β-strand	426-428	3	46
β-strand	431-436	6	40
α-helix	440-442	3
β-strand	443	1	47
α-helix	453-455	3
α-helix	456-468	13
β-strand	470	1	47
β-strand	471	1	32
α-helix	481-495	15
α-helix	500-505	6
α-helix	511-518	8
α-helix	521-529	9

Chain A: 23 helices, 28 β-strands

Element	Residues	Length	Sheet
α-helix	4-8	5
β-strand	36-43	8	1
α-helix	47-49	3
α-helix	59-77	19
β-strand	82-88	7	1
β-strand	94	1	1
β-strand	102-109	8	1
α-helix	113-120	8
α-helix	125-134	10
α-helix	143-156	14
β-strand	163-170	8	1
α-helix	180-196	17
β-strand	199-204	6	1
α-helix	205-206	2
β-strand	211-212	2	2
α-helix	213-216	4
α-helix	217-219	3
β-strand	231-232	2	2
α-helix	237-243	7
α-helix	251-253	3
β-strand	257-262	6	3
β-strand	268-274	7	3
β-strand	277	1	4
α-helix	282-285	4
β-strand	286-289	4	5
β-strand	295	1	5
β-strand	297-304	8	6
β-strand	310	1	6
β-strand	317-321	5	7
β-strand	326-329	4	7
α-helix	331-336	6
β-strand	344-352	9	3
α-helix	353-355	3
β-strand	366-370	5	3
β-strand	375-376	2	8
α-helix	378-392	15
β-strand	394-401	8	3
β-strand	409-416	8	3
β-strand	419-420	2	9
β-strand	426-428	3	9
β-strand	431-436	6	3
α-helix	440-442	3
β-strand	443	1	10
α-helix	445-448	4
α-helix	456-468	13
β-strand	470	1	10
β-strand	471	1	11
α-helix	481-495	15
α-helix	500-504	5
α-helix	511-517	7
α-helix	521-529	9

Chain b: 25 helices, 24 β-strands

Element	Residues	Length	Sheet
β-strand	9-15	7	48
α-helix	18-20	3
α-helix	30-47	18
β-strand	53-59	7	48
β-strand	65	1	48
β-strand	77-84	8	48
α-helix	88-92	5
α-helix	93-97	5
α-helix	107-122	16
β-strand	130-135	6	48
α-helix	147-157	11
β-strand	160-165	6	48
α-helix	199-215	17
α-helix	218-223	6
β-strand	224-226	3	48
α-helix	227-233	7
α-helix	237-240	4
α-helix	243-246	4
β-strand	247-253	7	47
β-strand	257-268	12	47
β-strand	277-279	3	44
β-strand	289-297	9	43
β-strand	304	1	43
α-helix	307-309	3
β-strand	310-316	7	42
β-strand	319-322	4	42
α-helix	325-331	7
α-helix	333-334	2
β-strand	339-347	9	47
α-helix	353-355	3
β-strand	357-366	10	47
α-helix	367	1
α-helix	371-387	17
β-strand	389-396	8	47
α-helix	402-403	2
β-strand	404-412	9	47
β-strand	417-423	7	47
β-strand	430	1	41
α-helix	445-447	3
α-helix	448-460	13
β-strand	462	1	40
β-strand	464-467	4	49
β-strand	472-475	4	49
α-helix	483-484	2
α-helix	485-499	15
α-helix	510-515	6
α-helix	520-525	6
α-helix	527-536	10
β-strand	540-541	2	45

Chain B: 26 helices, 24 β-strands

Element	Residues	Length	Sheet
β-strand	8-15	8	12
α-helix	18-21	4
α-helix	25-27	3
α-helix	30-47	18
β-strand	53-59	7	12
β-strand	65	1	12
β-strand	77-84	8	12
α-helix	88-92	5
α-helix	93-97	5
α-helix	107-120	14
β-strand	129-135	7	12
α-helix	147-157	11
β-strand	162-165	4	12
α-helix	199-215	17
α-helix	218-223	6
β-strand	224-226	3	12
α-helix	227-234	8
α-helix	237-239	3
α-helix	243-246	4
β-strand	247-253	7	10
β-strand	257-268	12	10
β-strand	277-279	3	7
β-strand	289-296	8	6
β-strand	304-305	2	6
α-helix	307-309	3
β-strand	310-316	7	5
β-strand	319-322	4	5
α-helix	325-331	7
β-strand	339-347	9	10
α-helix	348-350	3
α-helix	353-355	3
β-strand	357-366	10	10
α-helix	367	1
α-helix	371-387	17
β-strand	389-396	8	10
β-strand	404-412	9	10
β-strand	417-423	7	10
β-strand	430	1	4
α-helix	448-460	13
β-strand	462	1	3
β-strand	464-466	3	13
β-strand	473-475	3	13
α-helix	479-481	3
α-helix	483-484	2
α-helix	485-499	15
α-helix	504-505	2
α-helix	507-509	3
α-helix	510-515	6
α-helix	520-536	17
β-strand	540-541	2	8

Chain c: 12 helices, 9 β-strands

Element	Residues	Length	Sheet
α-helix	1-9	9
β-strand	14-18	5	50
β-strand	21-30	10	50
β-strand	33-39	7	50
β-strand	44-50	7	50
α-helix	51-61	11
β-strand	65-66	2	51
α-helix	69-85	17
β-strand	94-99	6	52
β-strand	104-111	8	52
β-strand	116-123	8	52
β-strand	124-125	2	50
α-helix	126-127	2
α-helix	128-131	4
α-helix	132-136	5
α-helix	137-170	34
α-helix	182-184	3
α-helix	186-196	11
α-helix	198-201	4
α-helix	208-213	6
α-helix	216-226	11

Chain C: 15 helices, 8 β-strands

Element	Residues	Length	Sheet
α-helix	1-10	10
α-helix	12-13	2
β-strand	14-17	4	14
β-strand	22-30	9	14
β-strand	33-39	7	14
β-strand	44-50	7	14
α-helix	51-61	11
β-strand	65	1	15
α-helix	69-85	17
β-strand	93-99	7	14
β-strand	103-112	10	14
β-strand	115-125	11	14
α-helix	126-127	2
α-helix	128-131	4
α-helix	132-136	5
α-helix	137-169	33
α-helix	177-179	3
α-helix	182-184	3
α-helix	186-196	11
α-helix	198-201	4
α-helix	208-213	6
α-helix	215-228	14
α-helix	296-298	3

Chain d: 3 helices, 11 β-strands

Element	Residues	Length	Sheet
β-strand	2-9	8	53
β-strand	10	1	54
β-strand	17-24	8	53
β-strand	31-37	7	53
β-strand	42-48	7	53
α-helix	49-59	11
α-helix	63-74	12
β-strand	84-89	6	54
β-strand	94-99	6	54
β-strand	101	1	55
β-strand	104	1	55
β-strand	107-112	6	54
β-strand	114-115	2	53
α-helix	119-199	81

Chain D: 4 helices, 10 β-strands

Element	Residues	Length	Sheet
β-strand	2-8	7	16
β-strand	18-24	7	16
β-strand	32-37	6	16
β-strand	42-47	6	16
α-helix	49-59	11
α-helix	63-71	9
α-helix	72-76	5
β-strand	85-89	5	17
β-strand	94-98	5	17
β-strand	101	1	18
β-strand	104	1	18
β-strand	107-112	6	17
β-strand	114-116	3	16
α-helix	119-201	83

8 more chain groups are not listed. Open the entry in the viewer and use the sequence panel to see them.

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
X-ray repair cross-complementing protein 6	A, a	protein	612	Homo sapiens	P12956 (AlphaFold model)
X-ray repair cross-complementing protein 5	B, b	protein	732	Homo sapiens	P13010 (AlphaFold model)
Non-homologous end-joining factor 1	C, c	protein	302	Homo sapiens	Q9H9Q4 (AlphaFold model)
DNA repair protein XRCC4	D, E, d, e	protein	336	Homo sapiens	Q13426 (AlphaFold model)
DNA ligase 4	F, f	protein	914	Homo sapiens	P49917
Protein PAXX	G, H	protein	218	Homo sapiens	Q9BUH6
DNA (38-mer)	I	DNA	68	Homo sapiens
DNA (42-mer)	J	DNA	68	Homo sapiens
DNA (34-mer)	K	DNA	51	Homo sapiens
DNA (37-mer)	L	DNA	50	Homo sapiens
DNA-directed DNA/RNA polymerase mu	M, m	protein	512	Homo sapiens	Q9NP87

Sequence of entity 1 (A, a), FASTA

>9N81_1 X-ray repair cross-complementing protein 6 (chains A, a)
GPVMSGWESYYKTEGDEEAEEEQEENLEASGDYKYSGRDSLIFLVDASKAMFESQSEDEL
TPFDMSIQCIQSVYISKIISSDRDLLAVVFYGTEKDKNSVNFKNIYVLQELDNPGAKRIL
ELDQFKGQQGQKRFQDMMGHGSDYSLSEVLWVCANLFSDVQFKMSHKRIMLFTNEDNPHG
NDSAKASRARTKAGDLRDTGIFLDLMHLKKPGGFDISLFYRDIISIAEDEDLRVHFEESS
KLEDLLRKVRAKETRKRALSRLKLKLNKDIVISVGIYNLVQKALKPPPIKLYRETNEPVK
TKTRTFNTSTGGLLLPSDTKRSQIYGSRQIILEKEETEELKRFDDPGLMLMGFKPLVLLK
KHHYLRPSLFVYPEESLVIGSSTLFSALLIKCLEKEVAALCRYTPRRNIPPYFVALVPQE
EELDDQKIQVTPPGFQLVFLPFADDKRKMPFTEKIMATPEQVGKMKAIVEKLRFTYRSDS
FENPVLQQHFRNLEALALDLMEPEQAVDLTLPKVEAMNKRLGSLVDEFKELVYPPDYNPE
GKVTKRKHDNEGSGSKRPKVEYSEEELKTHISKGTLGKFTVPMLKEACRAYGLKSGLKKQ
ELLEALTKHFQD

Sequence of entity 2 (B, b), FASTA

>9N81_2 X-ray repair cross-complementing protein 5 (chains B, b)
MVRSGNKAAVVLCMDVGFTMSNSIPGIESPFEQAKKVITMFVQRQVFAENKDEIALVLFG
TDGTDNPLSGGDQYQNITVHRHLMLPDFDLLEDIESKIQPGSQQADFLDALIVSMDVIQH
ETIGKKFEKRHIEIFTDLSSRFSKSQLDIIIHSLKKCDISLQFFLPFSLGKEDGSGDRGD
GPFRLGGHGPSFPLKGITEQQKEGLEIVKMVMISLEGEDGLDEIYSFSESLRKLCVFKKI
ERHSIHWPCRLTIGSNLSIRIAAYKSILQERVKKTWTVVDAKTLKKEDIQKETVYCLNDD
DETEVLKEDIIQGFRYGSDIVPFSKVDEEQMKYKSEGKCFSVLGFCKSSQVQRRFFMGNQ
VLKVFAARDDEAAAVALSSLIHALDDLDMVAIVRYAYDKRANPQVGVAFPHIKHNYECLV
YVQLPFMEDLRQYMFSSLKNSKKYAPTEAQLNAVDALIDSMSLAKKDEKTDTLEDLFPTT
KIPNPRFQRLFQCLLHRALHPREPLPPIQQHIWNMLNPPAEVTTKSQIPLSKIKTLFPLI
EAKKKDQVTAQEIFQDNHEDGPTAKKLKTEQGGAHFSVSSLAEGSVTSVGSVNPAENFRV
LVKQKKASFEEASNQLINHIEQFLDTNETPYFMKSIDCIRAFREEAIKFSEEQRFNNFLK
ALQEKVEIKQLNHFWEIVVQDGITLITKEEASGSSVTAEEAKKFLAPKDKPSGDTAAVFE
EGGDVDDLLDMI

Sequence of entity 3 (C, c), FASTA

>9N81_3 Non-homologous end-joining factor 1 (chains C, c)
GPVMEELEQGLLMQPWAWLQLAENSLLAKVFITKQGYALLVSDLQQVWHEQVDTSVVSQR
AKELNKRLTAPPAAFLCHLDNLLRPLLKDAAHPSEATFSCDCVADALILRVRSELSGLPF
YWNFHCMLASPSLVSQHLIRPLMGMSLALQCQVRELATLLHMKDLEIQDYQESGATLIRD
RLKTEPFEENSFLEQFMIEKLPEACSIGDGKPFVMNLQDLYMAVTTQEVQVGQKHQGAGD
PHTSNSASLQGIDSQCVNQPEQLVSSAPTLSAPEKESTGTSGPLQRPQLSKVKRKKPRGL
FS

Sequence of entity 4 (D, E, d, e), FASTA

>9N81_4 DNA repair protein XRCC4 (chains D, E, d, e)
MERKISRIHLVSEPSITHFLQVSWEKTLESGFVITLTDGHSAWTGTVSESEISQEADDMA
MEKGKYVGELRKALLSGAGPADVYTFNFSKESCYFFFEKNLKDVSFRLGSFNLEKVENPA
EVIRELICYCLDTIAENQAKNEHLQKENERLLRDWNDVQGRFEKCVSAKEALETDLYKRF
ILVLNEKKTKIRSLHNKLLNAAQEREKDIKQEGETAICSEMTADRDPVYDESTDEESENQ
TDLSGLASAAVSKDDSIISSLDVTDIAPSRKRRQRMQRNLGTEPKMAPQENQLQEKENSR
PDSSLPETSKKEHISAENMSLETLRNSSPEDLFDEI

Sequence of entity 5 (F, f), FASTA

>9N81_5 DNA ligase 4 (chains F, f)
GPVMAASQTSQTVASHVPFADLCSTLERIQKSKGRAEKIRHFREFLDSWRKFHDALHKNH
KDVTDSFYPAMRLILPQLERERMAYGIKETMLAKLYIELLNLPRDGKDALKLLNYRTPTG
THGDAGDFAMIAYFVLKPRCLQKGSLTIQQVNDLLDSIASNNSAKRKDLIKKSLLQLITQ
SSALEQKWLIRMIIKDLKLGVSQQTIFSVFHNDAAELHNVTTDLEKVCRQLHDPSVGLSD
ISITLFSAFKPMLAAIADIEHIEKDMKHQSFYIETKLDGERMQMHKDGDVYKYFSRNGYN
YTDQFGASPTEGSLTPFIHNAFKADIQICILDGEMMAYNPNTQTFMQKGTKFDIKRMVED
SDLQTCYCVFDVLMVNNKKLGHETLRKRYEILSSIFTPIPGRIEIVQKTQAHTKNEVIDA
LNEAIDKREEGIMVKQPLSIYKPDKRGEGWLKIKPEYVSGLMDELDILIVGGYWGKGSRG
GMMSHFLCAVAEKPPPGEKPSVFHTLSRVGSGCTMKELYDLGLKLAKYWKPFHRKAPPSS
ILCGTEKPEVYIEPCNSVIVQIKAAEIVPSDMYKTGCTLRFPRIEKIRDDKEWHECMTLD
DLEQLRGKASGKLASKHLYIGGDDEPQEKKRKAAPKMKKVIGIIEHLKAPNLTNVNKISN
IFEDVEFCVMSGTDSQPKPDLENRIAEFGGYIVQNPGPDTYCVIAGSENIRVKNIILSNK
HDVVKPAWLLECFKTKSFVPWQPRFMIHMCPSTKEHFAREYDCYGDSYFIDTDLNQLKEV
FSGIKNSNEQTPEEMASLIADLEYRYSWDCSPLSMFRRHTVYLDSYAVINDLSTKNEGTR
LAIKALELRFHGAKVVSCLAEGVSHVIIGEDHSRVADFKAFRRTFKRKFKILKESWVTDS
IDKCELQEENQYLI

Sequence of entity 6 (G, H), FASTA

>9N81_6 Protein PAXX (chains G, H)
MGSSHHHHHHSQDPMDPLSPPLCTLPPGPEPPRFVCYCEGEESGEGDRGGFNLYVTDAAE
LWSTCFTPDSLAALKARFGLSAAEDITPRFRAACEQQAVALTLQEDRASLTLSGGPSALA
FDLSKVPGPEAAPRLRALTLGLAKRVWSLERRLAAAEETAVSPRKSPRPAGPQLFLPDPD
PQRGGPGPGVRRRCPGESLINPGFKSKKPAGGVDFDET

Sequence of entity 7 (I), FASTA

>9N81_7 DNA (38-MER) (chains I)
CGCGCCCAGCTTTCCCAGCTAATAAACTAAAAACTATGCATGCTCTACTGCTTCTGATCT
AGTCGACT

Sequence of entity 8 (J), FASTA

>9N81_8 DNA (42-MER) (chains J)
CGCGCCCAGCTTTCCCAGCTAATAAACTAAAAACATTCGTTCACGTGAGTTCCAGTACAA
GTCTAGTC

Sequence of entity 9 (K), FASTA

>9N81_9 DNA (34-MER) (chains K)
GACTAGATCAGAAGCAGTAGAGCATGCATAGTTTTTAGTTTATTGGGCGCG

Sequence of entity 10 (L), FASTA

>9N81_10 DNA (37-MER) (chains L)
GACTTGTACTGGAACTCACGTGAACGAATGTTTTTAGTTTATTGGGCGCG

Sequence of entity 11 (M, m), FASTA

>9N81_11 DNA-directed DNA/RNA polymerase mu (chains M, m)
HHHHHHSSGLEVLFQGPHMLPKRRRARVGSPSGDAASSTPPSTRFPGVAIYLVEPRMGRS
RRAFLTGLARSKGFRVLDACSSEATHVVMEETSAEEAVSWQERRMAAAPPGCTPPALLDI
SWLTESLGAGQPVPVECRHRLEVAGPRKGPLSPAWMPAYACQRPTPLTHHNTGLSEALEI
LAEAAGFEGSEGRLLTFCRAASVLKALPSPVTTLSQLQGLPHFGEHSSRVVQELLEHGVC
EEVERVRRSERYQTMKLFTQIFGVGVKTADRWYREGLRTLDDLREQPQKLTQQQKAGLQH
HQDLSTPVLRSDVDALQQVVEEAVGQALPGATVTLTGGFRRGKLQGHDVDFLITHPKEGQ
EAGLLPRVMCRLQDQGLILYHQHQHSCCESPTRLAQQSHMDAFERSFCIFRLPQPPGAAV
GGSTRPCPSWKAVRVDLVVAPVSQFPFALLGWTGSKLFQRELRRFSRKEKGLWLNSHGLF
DPEQKTFFQAASEEDIFRHLGLEYLPPEQRNA

Ligands and cofactors

ID	Name	Formula	Copies
DZ4	2'-deoxy-5'-O-[(R)-hydroxy{[(R)-hydroxy(phosphonooxy)phosphoryl]amino}phosphory…	C10 H17 N6 O11 P3	1
MG	Magnesium ion	Mg	1

Primary citation

Dynamic assemblies and coordinated reactions of non-homologous end joining. Liu, L., Li, J., Cisneros-Aguirre, M. et al. Nature (2025) 643:847-854. DOI 10.1038/s41586-025-09078-9 · PubMed

Other PDB entries of the same protein (UniProt P12956 (AlphaFold model), which also has an AlphaFold model), best resolution first:

8AG4 2.46 Å, Vaccinia C16 protein bound to Ku70/Ku80
1JEY 2.5 Å, Crystal Structure of the Ku heterodimer bound to DNA
3RZX 2.61 Å, Mouse importin alpha-Ku70 NLS peptide complex
7ZYG 2.68 Å, CryoEM structure of Ku heterodimer bound to DNA, PAXX and XLF
1JEQ 2.7 Å, Crystal Structure of the Ku Heterodimer
7ZVT 2.74 Å, CryoEM structure of Ku heterodimer bound to DNA
6ERH 2.8 Å, Complex of XLF and heterodimer Ku bound to DNA
7ZWA 2.8 Å, CryoEM structure of Ku heterodimer bound to DNA and PAXX
9CQ3 2.8 Å, The gap-filling complex with Pol mu engaged in the NHEJ pathway
9GYF 2.8 Å, Ku70/80 with PAXX peptide mutation K193R
6ERG 2.9 Å, Complex of XLF and heterodimer Ku bound to DNA
7Z87 2.91 Å, DNA-PK in the active state

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