9ZBL: Actin, alpha cardiac muscle 1

Helical Reconstruction of the Human Cardiac F-Actin-Tropomyosin Complex. Determined by electron microscopy at 2.79 Å resolution. Released 14 Jan 2026.

Method: Electron microscopy
Resolution: 2.79 Å
Organism: Homo sapiens
Chains: 10
Atoms: 21,570
Mol. weight: 386.79 kDa
Ligands: MG, ADP
Released: 14 Jan 2026

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

Secondary structure: helices and β-sheets

9ZBL contains 152 α-helices and 118 β-strands across 10 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: 25 helices, 20 β-strands

Element	Residues	Length	Sheet
β-strand	8-12	5	1
β-strand	16-21	6	1
β-strand	29-32	4	1
β-strand	35-38	4	2
α-helix	41	1
β-strand	42	1	3
β-strand	53-54	2	2
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	2
β-strand	71-72	2	4
β-strand	75-76	2	4
α-helix	79-87	9
α-helix	88-93	6
α-helix	98-100	3
β-strand	103-107	5	1
α-helix	113-121	9
α-helix	122-126	5
β-strand	131-136	6	1
α-helix	137-144	8
β-strand	150-155	6	5
β-strand	160-166	7	5
β-strand	169-170	2	5
α-helix	172-174	3
β-strand	176-178	3	5
α-helix	182-194	13
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	6
β-strand	247-250	4	6
α-helix	253-256	4
α-helix	258-261	4
α-helix	264-267	4
α-helix	274-283	10
α-helix	290-295	6
β-strand	297-300	4	5
α-helix	303-305	3
α-helix	309-320	12
α-helix	326-327	2
β-strand	329-330	2	5
α-helix	338-348	11
α-helix	351-355	5
β-strand	357-358	2	1
α-helix	359-364	6
α-helix	369-373	5

Chain B: 24 helices, 20 β-strands

Element	Residues	Length	Sheet
β-strand	8-12	5	7
β-strand	16-21	6	7
β-strand	29-32	4	7
β-strand	35-38	4	8
β-strand	42	1	9
β-strand	53-54	2	8
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	8
β-strand	71-72	2	10
β-strand	75-76	2	10
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	103-107	5	7
α-helix	113-121	9
α-helix	122-126	5
β-strand	131-136	6	7
α-helix	137-144	8
β-strand	150-155	6	11
β-strand	160-166	7	11
β-strand	169-170	2	11
α-helix	172-174	3
β-strand	176-178	3	11
α-helix	182-193	12
α-helix	194-196	3
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	12
β-strand	247-250	4	12
α-helix	253-259	7
α-helix	264-267	4
α-helix	274-284	11
α-helix	287-295	9
β-strand	297-300	4	11
α-helix	303-305	3
α-helix	309-320	12
α-helix	326-327	2
β-strand	329-330	2	11
α-helix	338-348	11
α-helix	351-354	4
β-strand	357-358	2	7
α-helix	359-365	7
α-helix	369-373	5

Chain C: 27 helices, 20 β-strands

Element	Residues	Length	Sheet
α-helix	6-7	2
β-strand	8-12	5	13
β-strand	16-21	6	13
β-strand	29-32	4	13
β-strand	35-38	4	14
α-helix	41	1
β-strand	42	1	15
β-strand	53-54	2	14
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	14
β-strand	71-72	2	16
β-strand	75-76	2	16
α-helix	79-87	9
α-helix	88-93	6
α-helix	98-100	3
β-strand	103-107	5	13
α-helix	113-121	9
α-helix	122-126	5
β-strand	131-136	6	13
α-helix	137-144	8
β-strand	150-155	6	3
β-strand	160-166	7	3
β-strand	169-170	2	3
α-helix	172-174	3
β-strand	176-178	3	3
α-helix	182-193	12
α-helix	194-196	3
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	17
β-strand	247-250	4	17
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	297-300	4	3
α-helix	303-305	3
α-helix	309-320	12
β-strand	329-330	2	3
α-helix	335-337	3
α-helix	338-348	11
α-helix	351-354	4
β-strand	357-358	2	13
α-helix	359-364	6
α-helix	369-373	5

Chain D: 22 helices, 20 β-strands

Element	Residues	Length	Sheet
β-strand	8-12	5	18
β-strand	16-21	6	18
β-strand	29-32	4	18
β-strand	35-38	4	19
β-strand	42	1	20
β-strand	53-54	2	19
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	19
β-strand	71-72	2	21
β-strand	75-76	2	21
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	103-107	5	18
α-helix	113-125	13
β-strand	131-136	6	18
α-helix	137-144	8
β-strand	150-155	6	9
β-strand	160-166	7	9
β-strand	169-170	2	9
α-helix	172-174	3
β-strand	176-178	3	9
α-helix	182-194	13
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	22
β-strand	247-250	4	22
α-helix	253-256	4
α-helix	258-261	4
α-helix	264-267	4
α-helix	274-284	11
α-helix	287-294	8
β-strand	297-300	4	9
α-helix	303-305	3
α-helix	309-320	12
β-strand	329-330	2	9
α-helix	338-348	11
α-helix	351-354	4
β-strand	357-358	2	18
α-helix	359-364	6
α-helix	370-373	4

Chain E: 24 helices, 19 β-strands

Element	Residues	Length	Sheet
β-strand	8-12	5	23
β-strand	16-21	6	23
β-strand	29-32	4	23
β-strand	35-38	4	24
α-helix	41-42	2
β-strand	53-54	2	24
α-helix	56-60	5
β-strand	65-68	4	24
β-strand	71-72	2	25
β-strand	75-76	2	25
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	103-107	5	23
α-helix	113-121	9
α-helix	122-126	5
β-strand	131-136	6	23
α-helix	137-144	8
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	182-193	12
α-helix	194-196	3
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	26
β-strand	247-250	4	26
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	297-300	4	15
α-helix	303-305	3
α-helix	309-320	12
β-strand	329-330	2	15
α-helix	338-348	11
α-helix	351-354	4
β-strand	357-358	2	23
α-helix	359-364	6
α-helix	369-373	5

Chain F: 26 helices, 19 β-strands

Element	Residues	Length	Sheet
β-strand	8-12	5	27
β-strand	16-21	6	27
β-strand	29-32	4	27
β-strand	35-38	4	28
α-helix	41-42	2
β-strand	53-54	2	28
α-helix	56-60	5
α-helix	62-64	3
β-strand	65-68	4	28
β-strand	71-72	2	29
β-strand	75-76	2	29
α-helix	79-88	10
α-helix	89-93	5
α-helix	98-100	3
β-strand	103-107	5	27
α-helix	113-125	13
β-strand	131-136	6	27
α-helix	137-144	8
β-strand	150-155	6	20
β-strand	160-166	7	20
β-strand	169-170	2	20
α-helix	172-174	3
β-strand	176-178	3	20
α-helix	182-193	12
α-helix	194-196	3
α-helix	203-215	13
α-helix	223-231	9
β-strand	238-241	4	30
β-strand	247-250	4	30
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	297-300	4	20
α-helix	303-305	3
α-helix	309-320	12
α-helix	326-327	2
β-strand	329-330	2	20
α-helix	338-348	11
α-helix	351-354	4
β-strand	357-358	2	27
α-helix	359-364	6
α-helix	367-369	3
α-helix	370-373	4

Chains M, N, O and P: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	103-224	122

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Actin, alpha cardiac muscle 1	A, B, C, D, E, F	protein	377	Homo sapiens	P68032 (AlphaFold model)
Tropomyosin alpha-1 chain	M, N, O, P	protein	286	Homo sapiens	P09493 (AlphaFold model)

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

>9ZBL_1 Actin, alpha cardiac muscle 1 (chains A, B, C, D, E, F)
MCDDEETTALVCDNGSGLVKAGFAGDDAPRAVFPSIVGRPRHQGVMVGMGQKDSYVGDEA
QSKRGILTLKYPIEHGIITNWDDMEKIWHHTFYNELRVAPEEHPTLLTEAPLNPKANREK
MTQIMFETFNVPAMYVAIQAVLSLYASGRTTGIVLDSGDGVTHNVPIYEGYALPHAIMRL
DLAGRDLTDYLMKILTERGYSFVTTAEREIVRDIKEKLCYVALDFENEMATAASSSSLEK
SYELPDGQVITIGNERFRCPETLFQPSFIGMESAGIHETTYNSIMKCDIDIRKDLYANNV
LSGGTTMYPGIADRMQKEITALAPSTMKIKIIAPPERKYSVWIGGSILASLSTFQQMWIS
KQEYDEAGPSIVHRKCF

Sequence of entity 2 (M, N, O, P), FASTA

>9ZBL_2 Tropomyosin alpha-1 chain (chains M, N, O, P)
ASMDAIKKKMQMLKLDKENALDRAEQAEADKKAAEDRSKQLEDELVSLQKKLKGTEDELD
KYSEALKDAQEKLELAEKKATDAEADVASLNRRIQLVEEELDRAQERLATALQKLEEAEK
AADESERGMKVIESRAQKDEEKMEIQEIQLKEAKHIAEDADRKYEEVARKLVIIESDLER
AEERAELSEGKCAELEEELKTVTNNLKSLEAQAEKYSQKEDRYEEEIKVLSDKLKEAETR
AEFAERSVTKLEKSIDDLEDELYAQKLKYKAISEELDHALNDMTSI

Ligands and cofactors

ID	Name	Formula	Copies
MG	Magnesium ion	Mg	6
ADP	Adenosine-5'-diphosphate	C10 H15 N5 O10 P2	6

Primary citation

Pseudo-acetylation of ACTC1 K326 and K328 promotes dysinhibition of reconstituted human cardiac thin filaments. Chitre, K., Karpicheva, O.E., King, C.J. et al. J Mol Cell Cardiol (2025) 212:10-15. DOI 10.1016/j.yjmcc.2025.12.008 · PubMed

Other PDB entries of the same protein (UniProt P68032 (AlphaFold model), which also has an AlphaFold model), best resolution first:

8GT1 1.35 Å, Crystal structure of human cardiac alpha actin A108G mutant (ADP-Pi state) in complex…
8GSW 1.4 Å, Crystal structure of human cardiac alpha actin A108G mutant (AMPPNP state) in complex…
8GT5 1.4 Å, Crystal structure of human cardiac alpha actin Q137A mutant (ADP-Pi state) in complex…
8GSU 1.5 Å, Crystal structure of human cardiac alpha actin (WT_ADP-Pi) in complex with fragmin F1…
8GT2 1.5 Å, Crystal structure of human cardiac alpha actin P109A mutant (AMPPNP state) in complex…
8GT3 1.5 Å, Crystal structure of human cardiac alpha actin P109A mutant (ADP-Pi state) in complex…
8GT4 1.55 Å, Crystal structure of human cardiac alpha actin Q137A mutant (AMPPNP state) in complex…
8ZI9 3.08 Å, Human left ventricle actin and myosin complex
9BPH 3.12 Å, cryo-EM structure of cardiac muscle alpha-actin M305L hcm mutant
9ZBP 3.12 Å, Helical Reconstruction of the Complex of Pseudo-Acetylated Human Cardiac Actin…
8ZB7 3.19 Å, Human left ventricle ATM complex
9B3R 3.5 Å, The structure of human cardiac F-actin

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