9YK9: Actin, alpha cardiac muscle 1

The structure of the cardiac native crossbridge in the rigor state, myosin heads bound to actin molecules 1 and 2. Determined by electron microscopy at 4.5 Å resolution. Released 22 Jul 2026.

Method: Electron microscopy
Resolution: 4.5 Å
Organism: Sus scrofa
Chains: 13
Atoms: 30,678
Mol. weight: 825.93 kDa
Ligands: MG, ADP
Released: 22 Jul 2026

Explore 9YK9 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9YK9 contains 200 α-helices and 139 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: 23 helices, 19 β-strands

Element	Residues	Length	Sheet
β-strand	8-11	4	1
β-strand	16-21	6	1
β-strand	29-32	4	1
β-strand	35-38	4	2
β-strand	53-54	2	2
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	103-107	5	1
α-helix	114-125	12
β-strand	131-136	6	1
α-helix	139-144	6
β-strand	149-155	7	4
β-strand	160-166	7	4
β-strand	169-170	2	4
α-helix	172-174	3
β-strand	176-178	3	4
α-helix	182-191	10
α-helix	192-196	5
α-helix	203-205	3
α-helix	206-216	11
α-helix	223-232	10
β-strand	238-242	5	5
β-strand	245-250	6	5
α-helix	253-256	4
α-helix	258-261	4
α-helix	264-266	3
α-helix	274-283	10
α-helix	290-293	4
β-strand	297-300	4	4
α-helix	309-320	12
β-strand	329-330	2	4
α-helix	335-337	3
α-helix	340-346	7
α-helix	350-354	5
β-strand	357-358	2	1
α-helix	359-362	4
α-helix	366-371	6

Chain B: 24 helices, 20 β-strands

Element	Residues	Length	Sheet
β-strand	8-9	2	6
β-strand	10-11	2	7
β-strand	16-19	4	7
β-strand	29-32	4	7
β-strand	35-38	4	8
β-strand	53-54	2	8
α-helix	55-60	6
α-helix	62-64	3
β-strand	65-68	4	8
β-strand	71	1	9
β-strand	76	1	9
α-helix	79-88	10
α-helix	89-94	6
β-strand	103-107	5	6
α-helix	114-122	9
α-helix	123-127	5
β-strand	131-136	6	6
α-helix	137-144	8
β-strand	149-155	7	10
β-strand	160-166	7	10
β-strand	169-170	2	10
α-helix	172-174	3
β-strand	176-178	3	10
α-helix	182-192	11
α-helix	193-196	4
α-helix	206-216	11
α-helix	223-230	8
β-strand	238-242	5	11
β-strand	245-250	6	11
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	10
α-helix	303-305	3
α-helix	309-318	10
β-strand	329-330	2	10
α-helix	335-337	3
α-helix	338-348	11
α-helix	350-354	5
β-strand	357-358	2	6
α-helix	359-362	4
α-helix	366-371	6

Chain C: 24 helices, 19 β-strands

Element	Residues	Length	Sheet
β-strand	8-11	4	12
β-strand	16-21	6	12
β-strand	29-32	4	12
β-strand	35-38	4	13
β-strand	53-54	2	13
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	13
β-strand	71	1	14
β-strand	76	1	14
α-helix	80-88	9
α-helix	89-93	5
β-strand	103-107	5	12
α-helix	113-122	10
α-helix	123-127	5
β-strand	131-136	6	12
α-helix	137-145	9
β-strand	150-155	6	15
β-strand	160-166	7	15
β-strand	169-170	2	15
α-helix	172-174	3
β-strand	176-178	3	15
α-helix	182-192	11
α-helix	193-196	4
α-helix	206-215	10
α-helix	223-232	10
β-strand	238-242	5	16
β-strand	245-250	6	16
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	297-300	4	15
α-helix	302-304	3
α-helix	309-318	10
β-strand	329-330	2	15
α-helix	335-337	3
α-helix	338-346	9
α-helix	351-355	5
β-strand	357-358	2	12
α-helix	359-365	7
α-helix	367-371	5

Chain D: 23 helices, 21 β-strands

Element	Residues	Length	Sheet
β-strand	8-11	4	17
β-strand	16-21	6	17
β-strand	22	1	18
β-strand	24	1	18
β-strand	29-32	4	17
β-strand	35-38	4	19
β-strand	53-54	2	19
α-helix	55-59	5
β-strand	65-68	4	19
β-strand	71	1	20
β-strand	76	1	20
α-helix	79-88	10
α-helix	89-94	6
α-helix	98-100	3
β-strand	103-105	3	17
α-helix	114-125	12
β-strand	131-134	4	17
α-helix	137-144	8
β-strand	149-155	7	21
β-strand	160-166	7	21
β-strand	169-170	2	21
α-helix	172-174	3
β-strand	176-178	3	21
α-helix	184-192	9
α-helix	193-196	4
α-helix	203-205	3
α-helix	206-216	11
α-helix	223-232	10
β-strand	238-241	4	22
β-strand	247-250	4	22
α-helix	253-256	4
α-helix	258-261	4
α-helix	274-283	10
α-helix	287-289	3
α-helix	293-295	3
β-strand	297-300	4	21
α-helix	302-305	4
α-helix	309-320	12
β-strand	329-330	2	21
α-helix	338-346	9
α-helix	352-354	3
β-strand	357-358	2	17
α-helix	359-365	7
α-helix	367-369	3

Chain E: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	251-283	33

Chain F: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	251-281	31

Chain G: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	3-154	152

Chain H: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	2-154	153

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

Sequence of entity 1 (A, B, C, D), FASTA

>9YK9_1 Actin, alpha cardiac muscle 1 (chains A, B, C, D)
MCDDEETTALVCDNGSGLVKAGFAGDDAPRAVFPSIVGRPRHQGVMVGMGQKDSYVGDEA
QSKRGILTLKYPIEHGIITNWDDMEKIWHHTFYNELRVAPEEHPTLLTEAPLNPKANREK
MTQIMFETFNVPAMYVAIQAVLSLYASGRTTGIVLDSGDGVTHNVPIYEGYALPHAIMRL
DLAGRDLTDYLMKILTERGYSFVTTAEREIVRDIKEKLCYVALDFENEMATAASSSSLEK
SYELPDGQVITIGNERFRCPETLFQPSFIGMESAGIHETTYNSIMKCDIDIRKDLYANNV
LSGGTTMYPGIADRMQKEITALAPSTMKIKIIAPPERKYSVWIGGSILASLSTFQQMWIS
KQEYDEAGPSIVHRKCF

Sequence of entity 2 (E, F, G, H), FASTA

>9YK9_2 Tropomyosin alpha-1 chain (chains E, F, G, H)
MDAIKKKMQMLKLDKENALDRAEQAEADKKAAEDRSKRLEDELVSLQKKLKATEDELDKY
SEAPKDAQEKLELAEKKATDAEADVASLNRRIQLVEEELDRAQERLATALQKLEEAEKAA
DESERGMKVIESRAQKDEEKMEIQEIQLKEAKHIAEDADRKYEEVARKLVIIESDLERAE
ERAELSEGKCAELEEELKTVTNNLKSLEAQAEKYSQKEDKYEEEIKVLSDKLKEAETRAE
FAERSVTKLEKSIDDLEDELYAQKLKYKAISEELDHALNDMTSI

Sequence of entity 3 (I), FASTA

>9YK9_3 Troponin T2, cardiac type (chains I)
MSDVEETVDEYEEEQEEGAAEEQEEAVEEEAGGEAEAEEANAEEAGQEEDGREAEDGPME
ESKPKPRLFMPNLVPPKIPDGERVDFDDIHRKRMKDLNELQTLIEAHFENRKKEEELVSL
KDRIEKRRAERAEQQRIRTEREKERQTRLAEERARREEEENRRKAEDEARKKKALSNMMH
FGGYIQKQAQTERKSGKRQTEREKKKKILAERRKVLAIDHLNEDQLREKAKELWQSIYNL
EAEKFDLQEKFKQQKYEINVLRNRINDNQKVSKTRGKAKVTGRWK

Sequence of entity 4 (J, K), FASTA

>9YK9_4 Myosin-7 (chains J, K)
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 (L, M), FASTA

>9YK9_5 Myosin light chain 3 (chains L, M)
MAPKKPEPKKDDAKAAAKAAPAPAPAPAPAPEPKEPEFDASKIKIEFTPEQIEEFKEAFM
LFDRTPKCEMKITYGQCGDVLRALGQNPTQAEVLRVLGKPKQEELNSKMMDFDTFLPMLQ
HISKNKDTGTYEDFVEGLRVFDKEGNGTVMGAELRHVLATLGERLTEDEVEKLMAGQEDS
NGCINYEAFVKHIMAS

Ligands and cofactors

ID	Name	Formula	Copies
MG	Magnesium ion	Mg	4
ADP	Adenosine-5'-diphosphate	C10 H15 N5 O10 P2	4

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…
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…
9YKN 5.3 Å, The structure of the cardiac native crossbridge in the rigor state, myosin heads with…
7LRG 6.1 Å, Filamentous actin decorated with human cardiac myosin binding protein C C2 domain

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