9YKN: Actin, alpha cardiac muscle 1

The structure of the cardiac native crossbridge in the rigor state, myosin heads with essential and regulatory light chains bound to actin molecules 6 and 7. Determined by electron microscopy at 5.3 Å resolution. Released 22 Jul 2026.

Method: Electron microscopy
Resolution: 5.3 Å
Organism: Sus scrofa
Chains: 13
Atoms: 26,677
Mol. weight: 778.73 kDa
Ligands: MG, ADP
Released: 22 Jul 2026

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

Secondary structure: helices and β-sheets

9YKN contains 162 α-helices and 109 β-strands across 13 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: 22 helices, 21 β-strands

Element	Residues	Length	Sheet
β-strand	9-11	3	1
β-strand	16-20	5	1
β-strand	29-32	4	1
β-strand	35-38	4	2
β-strand	53-54	2	2
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	2
β-strand	71	1	3
β-strand	76	1	3
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	104	1	1
β-strand	105-107	3	4
α-helix	113-126	14
β-strand	131-132	2	5
β-strand	134-136	3	4
α-helix	137-144	8
β-strand	150-153	4	6
β-strand	160-166	7	6
β-strand	169-170	2	6
β-strand	176-178	3	6
α-helix	182-192	11
α-helix	193-195	3
α-helix	203-216	14
α-helix	223-232	10
β-strand	238-242	5	7
β-strand	245-250	6	7
α-helix	253-256	4
α-helix	258-261	4
α-helix	264-266	3
α-helix	274-283	10
α-helix	290-295	6
β-strand	297-299	3	6
α-helix	302-305	4
α-helix	309-320	12
β-strand	329-330	2	6
α-helix	338-348	11
α-helix	352-355	4
β-strand	357-358	2	5
α-helix	359-363	5
α-helix	367-371	5

Chain B: 25 helices, 20 β-strands

Element	Residues	Length	Sheet
β-strand	9	1	8
β-strand	10-11	2	9
β-strand	16-19	4	9
β-strand	29-32	4	9
β-strand	35-38	4	10
β-strand	53-54	2	10
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	10
β-strand	71	1	11
β-strand	76	1	11
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	103-107	5	8
α-helix	113-122	10
α-helix	123-127	5
β-strand	131-136	6	8
α-helix	137-144	8
β-strand	150-153	4	12
β-strand	160-166	7	12
β-strand	169-170	2	12
α-helix	172-174	3
β-strand	176-178	3	12
α-helix	182-192	11
α-helix	193-196	4
α-helix	203-216	14
α-helix	223-232	10
β-strand	238-242	5	13
β-strand	245-250	6	13
α-helix	253-256	4
α-helix	258-261	4
α-helix	264-267	4
α-helix	274-284	11
α-helix	290-295	6
β-strand	297-299	3	12
α-helix	302-304	3
α-helix	309-320	12
β-strand	329-330	2	12
α-helix	335-337	3
α-helix	338-347	10
α-helix	351-354	4
β-strand	357-358	2	8
α-helix	359-363	5
α-helix	367-371	5

Chain C: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	211-283	73

Chain D: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	211-282	72

Chains E and F: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	2-39	38

Chain G: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	86-149	64

Chain H: 37 helices, 27 β-strands

Element	Residues	Length	Sheet
α-helix	6-8	3
α-helix	20-28	9
β-strand	36-39	4	14
β-strand	47-54	8	14
β-strand	58-63	6	14
β-strand	68-72	5	14
α-helix	73-75	3
β-strand	77-78	2	14
α-helix	79-81	3
α-helix	82-84	3
β-strand	89	1	15
α-helix	98-110	13
β-strand	115-118	4	15
β-strand	121-125	5	15
α-helix	132-134	3
α-helix	136-141	6
α-helix	154-168	15
β-strand	172-177	6	15
α-helix	181-201	21
α-helix	207-209	3
α-helix	216-231	16
β-strand	232-233	2	16
β-strand	241-242	2	16
β-strand	245-252	8	15
β-strand	258-266	9	15
α-helix	270-273	4
α-helix	284-290	7
α-helix	295-300	6
α-helix	307-309	3
α-helix	327-338	12
α-helix	343-359	17
β-strand	364-366	3	17
β-strand	373-375	3	17
α-helix	379-388	10
α-helix	392-398	7
β-strand	403-406	4	18
β-strand	409-412	4	18
α-helix	417-446	30
β-strand	455-462	8	15
α-helix	473-504	32
α-helix	515-525	11
α-helix	530-536	7
α-helix	537-539	3
α-helix	545-556	12
β-strand	563-564	2	19
β-strand	577-580	4	19
β-strand	585-588	4	19
α-helix	593-597	5
β-strand	598	1	20
α-helix	603-610	8
α-helix	615-620	6
β-strand	646	1	20
α-helix	647-662	16
β-strand	666-673	8	15
α-helix	686-696	11
α-helix	698-707	10
β-strand	711-714	4	21
α-helix	715-722	8
α-helix	723-725	3
α-helix	738-746	9
β-strand	756-758	3	21
β-strand	762-765	4	21
α-helix	769-826	58
α-helix	828-836	9

Chain I: 35 helices, 27 β-strands

Element	Residues	Length	Sheet
α-helix	13-16	4
α-helix	20-26	7
β-strand	36-39	4	22
β-strand	47-54	8	22
β-strand	58-63	6	22
β-strand	68-72	5	22
β-strand	77-78	2	22
α-helix	79-81	3
α-helix	82-84	3
β-strand	89	1	23
α-helix	90-92	3
α-helix	98-110	13
β-strand	115-118	4	23
β-strand	121-125	5	23
α-helix	132-134	3
α-helix	136-141	6
α-helix	147-149	3
α-helix	154-168	15
β-strand	172-177	6	23
α-helix	181-200	20
α-helix	218-231	14
β-strand	232-233	2	24
β-strand	241-242	2	24
β-strand	245-252	8	23
β-strand	258-266	9	23
α-helix	271-273	3
α-helix	284-290	7
α-helix	295-301	7
α-helix	325-339	15
α-helix	343-359	17
β-strand	364-366	3	25
α-helix	367	1
β-strand	373-375	3	25
α-helix	379-387	9
α-helix	392-400	9
β-strand	403-406	4	26
β-strand	409-412	4	26
α-helix	417-446	30
β-strand	455-461	7	23
α-helix	473-504	32
α-helix	515-525	11
α-helix	530-537	8
α-helix	545-556	12
β-strand	563-564	2	27
β-strand	577-580	4	27
β-strand	585-588	4	27
α-helix	593-597	5
β-strand	598	1	28
α-helix	605-610	6
α-helix	615-620	6
β-strand	646	1	28
α-helix	647-663	17
β-strand	666-673	8	23
α-helix	686-696	11
α-helix	698-707	10
β-strand	711-714	4	29
α-helix	715-720	6
α-helix	738-746	9
β-strand	756-758	3	29
β-strand	762-765	4	29
α-helix	769-823	55
α-helix	828-835	8

4 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
Actin, alpha cardiac muscle 1	A, B	protein	377	Sus scrofa	B6VNT8 (AlphaFold model)
Tropomyosin alpha-1 chain	C, D, E, F	protein	284	Sus scrofa	P42639 (AlphaFold model)
Troponin T2, cardiac type	G	protein	285	Sus scrofa	A0A5G2Q8N0 (AlphaFold model)
Myosin-7	H, I	protein	1935	Sus scrofa	P79293 (AlphaFold model)
Myosin light chain 3	J, K	protein	196	Sus scrofa	F1SNW4
MYL2	L, M	protein	166	Sus scrofa	Q8MHY0

Sequence of entity 1 (A, B), FASTA

>9YKN_1 Actin, alpha cardiac muscle 1 (chains A, B)
MCDDEETTALVCDNGSGLVKAGFAGDDAPRAVFPSIVGRPRHQGVMVGMGQKDSYVGDEA
QSKRGILTLKYPIEHGIITNWDDMEKIWHHTFYNELRVAPEEHPTLLTEAPLNPKANREK
MTQIMFETFNVPAMYVAIQAVLSLYASGRTTGIVLDSGDGVTHNVPIYEGYALPHAIMRL
DLAGRDLTDYLMKILTERGYSFVTTAEREIVRDIKEKLCYVALDFENEMATAASSSSLEK
SYELPDGQVITIGNERFRCPETLFQPSFIGMESAGIHETTYNSIMKCDIDIRKDLYANNV
LSGGTTMYPGIADRMQKEITALAPSTMKIKIIAPPERKYSVWIGGSILASLSTFQQMWIS
KQEYDEAGPSIVHRKCF

Sequence of entity 2 (C, D, E, F), FASTA

>9YKN_2 Tropomyosin alpha-1 chain (chains C, D, E, F)
MDAIKKKMQMLKLDKENALDRAEQAEADKKAAEDRSKRLEDELVSLQKKLKATEDELDKY
SEAPKDAQEKLELAEKKATDAEADVASLNRRIQLVEEELDRAQERLATALQKLEEAEKAA
DESERGMKVIESRAQKDEEKMEIQEIQLKEAKHIAEDADRKYEEVARKLVIIESDLERAE
ERAELSEGKCAELEEELKTVTNNLKSLEAQAEKYSQKEDKYEEEIKVLSDKLKEAETRAE
FAERSVTKLEKSIDDLEDELYAQKLKYKAISEELDHALNDMTSI

Sequence of entity 3 (G), FASTA

>9YKN_3 Troponin T2, cardiac type (chains G)
MSDVEETVDEYEEEQEEGAAEEQEEAVEEEAGGEAEAEEANAEEAGQEEDGREAEDGPME
ESKPKPRLFMPNLVPPKIPDGERVDFDDIHRKRMKDLNELQTLIEAHFENRKKEEELVSL
KDRIEKRRAERAEQQRIRTEREKERQTRLAEERARREEEENRRKAEDEARKKKALSNMMH
FGGYIQKQAQTERKSGKRQTEREKKKKILAERRKVLAIDHLNEDQLREKAKELWQSIYNL
EAEKFDLQEKFKQQKYEINVLRNRINDNQKVSKTRGKAKVTGRWK

Sequence of entity 4 (H, I), FASTA

>9YKN_4 Myosin-7 (chains H, I)
MVDAEMAAFGEAAPYLRKSEKERLEAQTRPFDLKKDVYVPDDKEEFVKAKILSREGGKVT
AETEHGKTVTVKEDQVLQQNPPKFDKIEDMAMLTFLHEPAVLYNLKERYASWMIYTYSGL
FCVTINPYKWLPVYNAEVVAAYRGKKRSEAPPHIFSISDNAYQYMLTDRENQSILITGES
GAGKTVNTKRVIQYFAVIAAIGDRSKKEQTPGKGTLEDQIIQANPALEAFGNAKTVRNDN
SSRFGKFIRIHFGATGKLASADIETYLLEKSRVIFQLKAERDYHIFYQILSNKKPELLDM
LLITNNPYDYAFISQGETTVASIDDAEELMATDNAFDVLGFTSEEKNSMYKLTGAIMHFG
NMKFKLKQREEQAEPDGTEEADKSAYLMGLNSADLLKGLCHPRVKVGNEYVTKGQNVQQV
MYATGALAKAVYEKMFNWMVTRINTTLETKQPRQYFIGVLDIAGFEIFDFNSFEQLCINF
TNEKLQQFFNHHMFVLEQEEYKKEGIEWEFIDFGMDLQACIDLIEKPMGIMSILEEECMF
PKATDMTFKAKLYDNHLGKSNNFQKPRNIKGRPEAHFALIHYAGTVDYNIIGWLQKNKDP
LNETVVDLYKKSSLKLLSNLFANYAGADTPVEKGKGKAKKGSSFQTVSALHRENLNKLMT
NLRSTHPHFVRCIIPNETKSPGVIDNPLVMHQLRCNGVLEGIRICRKGFPNRILYGDFRQ
RYRILNPAAIPEGQFIDSRKGAEKLLGSLDIDHNQYKFGHTKVFFKAGLLGLLEEMRDER
LSRIITRIQAQSRGVLSRMEFKKLLERRDSLLIIQWNIRAFMSVKNWPWMKLYFKIKPLL
KSAETEKEMATMKEEFGRLKEALEKSEARRKELEEKMVSLLQEKNDLQLQVQAEQDNLAD
AEERCDQLIKNKIQLEAKVKEMTERLEDEEEMNAELTAKKRKLEDECSELKRDIDDLELT
LAKVEKEKHATENKVKNLTEEMAGLDEIIAKLTKEKKALQEAHQQALDDLQAEEDKVNTL
TKAKVKLEQHVDDLEGSLEQEKKVRMDLERAKRKLEGDLKLTQESIMDLENDKQQLDERL
KKKDFELNALNARIEDEQALGSQLQKKLKELQARIEELEEELEAERTARAKVEKLRSDLS
RELEEISERLEEAGGATSVQIEMNKKREAEFQKMRRDLEEATLQHEATAAALRKKHADSV
AELGEQIDNLQRVKQKLEKEKSEFKLELDDVTSNMEQIIKAKANLEKMCRTLEDQMNEHR
SKAEETQRSVNDLTSQRAKLQTENGELSRQLDEKEALISQLTRGKLTYTQQLEDLKRQLE
EEVKAKNALAHALQSARHDCDLLREQYEEETEAKAELQRVLSKANSEVAQWRTKYETDAI
QRTEELEEAKKKLAQRLQDAEEAVEAVNAKCSSLEKTKHRLQNEIEDLMVDVERSNAAAA
ALDKKQRNFDKILAEWKQKYEESQSELESSQKEARSLSTELFKLKNAYEESLEHLETFKR
ENKNLQEEISDLTEQLGSSGKTIHELEKVRKQLEAEKLELQSALEEAEASLEHEEGKILR
AQLEFNQIKAEMERKLAEKDEEMEQAKRNHLRVVDSLQTSLDAETRSRNEALRVKKKMEG
DLNEMEIQLSHANRMAAEAQKQVKSLQSLLKDTQIQLDDAVRANDDLKENIAIVERRNNL
LQAELEELRAVVEQTERSRKLAEQELIETSERVQLLHSQNTSLINQKKKMEADLSQLQTE
VEEAVQECRNAEEKAKKAITDAAMMAEELKKEQDTSAHLERMKKNMEQTIKDLQHRLDEA
EQIALKGGKKQLQKLEARVRELENELEAEQKRNAESVKGMRKSERRIKELTYQTEEDRKN
LLRLQDLVDKLQLKVKAYKRQAEEAEEQANTNLSKFRKVQHELDEAEERADIAESQVNKL
RAKSRDIGTKGLNEE

Sequence of entity 5 (J, K), FASTA

>9YKN_5 Myosin light chain 3 (chains J, K)
MAPKKPEPKKDDAKAAAKAAPAPAPAPAPAPEPKEPEFDASKIKIEFTPEQIEEFKEAFM
LFDRTPKCEMKITYGQCGDVLRALGQNPTQAEVLRVLGKPKQEELNSKMMDFDTFLPMLQ
HISKNKDTGTYEDFVEGLRVFDKEGNGTVMGAELRHVLATLGERLTEDEVEKLMAGQEDS
NGCINYEAFVKHIMAS

Sequence of entity 6 (L, M), FASTA

>9YKN_6 MYL2 (chains L, M)
MSPKKAKKRADGANSNVFSMFEQTQIQEFKEAFTIMDQNRDGFIDKNDLRDTFAALGRVN
VKNEEIDEMIKEAPGPINFTVFLTMFGEKLKGADPEETILNAFKVFDPEGKGVLRADYVK
EMLTTQAERFSKEEIEQMFAAFPPDVTGNLDYKNLVHIITHGEEKD

Ligands and cofactors

ID	Name	Formula	Copies
MG	Magnesium ion	Mg	2
ADP	Adenosine-5'-diphosphate	C10 H15 N5 O10 P2	2

Primary citation

The structure of the native cardiac crossbridge in the rigor state. Risi, C.M., Nguyen, T., Belknap, B. et al. Sci Adv (2026) 12:eaeg1209-eaeg1209. DOI 10.1126/sciadv.aeg1209 · PubMed

Other PDB entries of the same protein (UniProt B6VNT8 (AlphaFold model), which also has an AlphaFold model), best resolution first:

8EFI 3.4 Å, Helical reconstruction of the human cardiac actin-tropomyosin-myosin complex in the…
8ENC 3.6 Å, Helical reconstruction of the human cardiac actin-tropomyosin-myosin loop 4 7G mutant…
7JH7 3.8 Å, cardiac actomyosin complex
9YA8 4.32 Å, The structure of the cardiac native crossbridge in the rigor state, myosin heads bound…
9YK9 4.5 Å, The structure of the cardiac native crossbridge in the rigor state, myosin heads bound…
9YAQ 4.63 Å, The structure of the cardiac native cross bridge in the rigor state, myosin heads bound…
9YJP 4.8 Å, The structure of the cardiac native crossbridge in the rigor state, myosin heads bound…
7LRG 6.1 Å, Filamentous actin decorated with human cardiac myosin binding protein C C2 domain

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