9LZJ: Photosystem I P700 chlorophyll a apoprotein A1

The PSI3-IsiA43 complex with a closed double ring of IsiA proteins bound to a trimeric PSI core. Determined by electron microscopy at 3.4 Å resolution. Released 31 Dec 2025.

Method: Electron microscopy
Resolution: 3.4 Å
Organism: Thermosynechococcus vestitus BP-1
Chains: 79
Atoms: 235,011
Mol. weight: 3566.28 kDa
Ligands: CLA, PQN, SF4, BCR
Released: 31 Dec 2025

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

Secondary structure: helices and β-sheets

9LZJ contains 1,109 α-helices and 477 β-strands across 79 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: 17 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	24-26	3
α-helix	28-33	6
α-helix	39-66	28
α-helix	82-88	7
β-strand	92	1	85
β-strand	94	1	86
β-strand	98	1	85
α-helix	102-127	26
α-helix	139-143	5
α-helix	150-176	27
β-strand	181-183	3	86
β-strand	188-190	3	86
α-helix	199-204	6
α-helix	215-238	24
α-helix	240-241	2
α-helix	243-248	6
α-helix	253-277	25
α-helix	284-287	4
α-helix	290-291	2
β-strand	292-295	4	87
β-strand	299-302	4	87
α-helix	308-310	3
α-helix	314-341	28
α-helix	345-352	8

Chain a1: 17 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	28-33	6
α-helix	39-66	28
α-helix	82-87	6
β-strand	92	1	98
β-strand	94	1	99
β-strand	98	1	98
α-helix	102-123	22
α-helix	124-128	5
α-helix	140-143	4
α-helix	150-176	27
β-strand	181-183	3	99
β-strand	188-190	3	99
α-helix	199-203	5
α-helix	204-206	3
α-helix	215-238	24
α-helix	240-242	3
α-helix	243-248	6
α-helix	253-277	25
α-helix	284-287	4
β-strand	292-295	4	100
β-strand	299-302	4	100
α-helix	308-310	3
α-helix	314-341	28
α-helix	348-350	3

Chain a2: 18 helices, 6 β-strands

Element	Residues	Length	Sheet
α-helix	28-37	10
α-helix	39-66	28
α-helix	82-87	6
β-strand	92	1	106
β-strand	98	1	106
α-helix	102-123	22
α-helix	124-128	5
α-helix	139-142	4
α-helix	150-176	27
β-strand	181-183	3	107
β-strand	188-190	3	107
α-helix	199-203	5
α-helix	204-206	3
α-helix	215-238	24
α-helix	240-241	2
α-helix	243-248	6
α-helix	253-277	25
α-helix	290-291	2
β-strand	292-295	4	108
β-strand	299-302	4	108
α-helix	308-310	3
α-helix	311-313	3
α-helix	314-341	28
α-helix	347-350	4

Chain a3: 18 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	28-35	8
α-helix	39-66	28
α-helix	82-87	6
β-strand	92	1	116
β-strand	94	1	117
β-strand	98	1	116
α-helix	102-123	22
α-helix	124-128	5
α-helix	139-142	4
α-helix	150-176	27
β-strand	181-183	3	117
β-strand	188-190	3	117
α-helix	199-203	5
α-helix	204-206	3
α-helix	215-238	24
α-helix	240-242	3
α-helix	243-248	6
α-helix	253-277	25
α-helix	284-287	4
α-helix	290-291	2
β-strand	292-295	4	118
β-strand	299-302	4	118
α-helix	308-310	3
α-helix	314-341	28
α-helix	346-351	6

Chain a4: 17 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	28-33	6
α-helix	39-66	28
α-helix	82-88	7
β-strand	92	1	123
β-strand	94	1	124
β-strand	98	1	123
α-helix	102-123	22
α-helix	124-128	5
α-helix	139-143	5
α-helix	150-176	27
β-strand	181-183	3	124
β-strand	188-190	3	124
α-helix	199-204	6
α-helix	215-238	24
α-helix	240-242	3
α-helix	243-248	6
α-helix	253-277	25
α-helix	284-287	4
α-helix	290-291	2
β-strand	292-295	4	125
β-strand	299-302	4	125
α-helix	308-310	3
α-helix	314-340	27
α-helix	345-347	3

Chain a5: 17 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	28-36	9
α-helix	39-66	28
α-helix	82-88	7
β-strand	92	1	130
β-strand	94	1	131
β-strand	98	1	130
α-helix	102-123	22
α-helix	124-128	5
α-helix	139-143	5
α-helix	150-176	27
β-strand	181-183	3	131
β-strand	188-190	3	131
α-helix	199-203	5
α-helix	204-206	3
α-helix	215-238	24
α-helix	240-242	3
α-helix	243-248	6
α-helix	253-277	25
α-helix	284-287	4
α-helix	290-291	2
β-strand	292-295	4	132
β-strand	299-302	4	132
α-helix	314-340	27
α-helix	347-351	5

Chain a6: 15 helices, 7 β-strands

Element	Residues	Length	Sheet
α-helix	28-33	6
α-helix	39-67	29
α-helix	82-88	7
β-strand	92	1	136
β-strand	94	1	137
β-strand	98	1	136
α-helix	102-123	22
α-helix	124-128	5
α-helix	138-141	4
α-helix	150-176	27
β-strand	181-183	3	137
β-strand	188-190	3	137
α-helix	199-203	5
α-helix	215-238	24
α-helix	240-242	3
α-helix	243-248	6
α-helix	253-277	25
α-helix	290-291	2
β-strand	292-295	4	138
β-strand	299-302	4	138
α-helix	314-341	28
α-helix	346-349	4

Chain aA: 48 helices, 19 β-strands

Element	Residues	Length	Sheet
β-strand	16-18	3	1
α-helix	27-29	3
α-helix	37-40	4
β-strand	44	1	2
α-helix	46-53	8
α-helix	58-61	4
α-helix	65-96	32
β-strand	98	1	3
α-helix	100-105	6
α-helix	111-112	2
β-strand	113-114	2	3
α-helix	123-126	4
β-strand	128-129	2	4
β-strand	135-136	2	4
β-strand	137-138	2	3
α-helix	143-150	8
α-helix	155-177	23
α-helix	178-182	5
β-strand	183-185	3	1
α-helix	187-190	4
α-helix	193-198	6
α-helix	199-206	8
α-helix	207-215	9
α-helix	216-220	5
α-helix	221-229	9
α-helix	237-238	2
α-helix	241-244	4
α-helix	246-251	6
α-helix	265-268	4
α-helix	272-275	4
α-helix	294-312	19
β-strand	315	1	5
β-strand	323	1	5
α-helix	325-331	7
α-helix	344-348	5
α-helix	352-374	23
α-helix	387-414	28
α-helix	415-419	5
α-helix	429-435	7
α-helix	437-451	15
α-helix	452-456	5
α-helix	457-467	11
α-helix	471-473	3
α-helix	485-495	11
β-strand	498	1	6
β-strand	502	1	6
β-strand	518-520	3	7
β-strand	523-526	4	7
α-helix	528-531	4
α-helix	533-558	26
α-helix	569-572	4
β-strand	578	1	8
β-strand	587	1	8
α-helix	591-616	26
α-helix	617-621	5
β-strand	623-625	3	7
β-strand	631-633	3	7
α-helix	639-642	4
α-helix	646-648	3
α-helix	649-655	7
α-helix	656-657	2
α-helix	659-662	4
α-helix	670-691	22
α-helix	694-710	17
β-strand	718	1	2
α-helix	721-723	3
α-helix	724-754	31

59 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
Photosystem I P700 chlorophyll a apoprotein A1	aA, bA, cA	protein	755	Thermosynechococcus vestitus BP-1	P0A405 (AlphaFold model)
Photosystem I P700 chlorophyll a apoprotein A2	aB, bB, cB	protein	741	Thermosynechococcus vestitus BP-1	P0A407 (AlphaFold model)
Photosystem I iron-sulfur center	aC, bC, cC	protein	81	Thermosynechococcus vestitus BP-1	P0A415 (AlphaFold model)
Photosystem I reaction center subunit II	aD, bD, cD	protein	139	Thermosynechococcus vestitus BP-1	P0A420 (AlphaFold model)
Photosystem I reaction center subunit IV	aE, bE, cE	protein	76	Thermosynechococcus vestitus BP-1	P0A423
Photosystem I reaction center subunit III	aF, bF, cF	protein	164	Thermosynechococcus vestitus BP-1	P0A401
Photosystem I reaction center subunit VIII	aI, bI, cI	protein	38	Thermosynechococcus vestitus BP-1	P0A427
Photosystem I reaction center subunit IX	aJ, bJ, cJ	protein	41	Thermosynechococcus vestitus BP-1	P0A429
Photosystem I reaction center subunit PsaK	aK, bK, cK	protein	83	Thermosynechococcus vestitus BP-1	P0A425
Photosystem I reaction center subunit XI	aL, bL, cL	protein	155	Thermosynechococcus vestitus BP-1	Q8DGB4
Photosystem I reaction center subunit XII	aM, bM, cM	protein	31	Thermosynechococcus vestitus BP-1	P0A403
Photosystem I 4.8K protein	aX, bX, cX	protein	39	Thermosynechococcus vestitus BP-1	Q8DKP6

1 more molecules are not listed.

Sequence of entity 1 (aA, bA, cA), FASTA

>9LZJ_1 Photosystem I P700 chlorophyll a apoprotein A1 (chains aA, bA, cA)
MTISPPEREPKVRVVVDNDPVPTSFEKWAKPGHFDRTLARGPQTTTWIWNLHALAHDFDT
HTSDLEDISRKIFSAHFGHLAVVFIWLSGMYFHGAKFSNYEAWLADPTGIKPSAQVVWPI
VGQGILNGDVGGGFHGIQITSGLFQLWRASGITNEFQLYCTAIGGLVMAGLMLFAGWFHY
HKRAPKLEWFQNVESMLNHHLAGLLGLGSLAWAGHQIHVSLPINKLLDAGVAAKDIPLPH
EFILNPSLMAELYPKVDWGFFSGVIPFFTFNWAAYSDFLTFNGGLNPVTGGLWLSDTAHH
HLAIAVLFIIAGHMYRTNWGIGHSLKEILEAHKGPFTGAGHKGLYEVLTTSWHAQLAINL
AMMGSLSIIVAQHMYAMPPYPYLATDYPTQLSLFTHHMWIGGFLVVGGAAHGAIFMVRDY
DPAMNQNNVLDRVLRHRDAIISHLNWVCIFLGFHSFGLYVHNDTMRAFGRPQDMFSDTGI
QLQPVFAQWVQNLHTLAPGGTAPNAAATASVAFGGDVVAVGGKVAMMPIVLGTADFMVHH
IHAFTIHVTVLILLKGVLFARSSRLIPDKANLGFRFPCDGPGRGGTCQVSGWDHVFLGLF
WMYNCISVVIFHFSWKMQSDVWGTVAPDGTVSHITGGNFAQSAITINGWLRDFLWAQASQ
VIGSYGSALSAYGLLFLGAHFIWAFSLMFLFSGRGYWQELIESIVWAHNKLKVAPAIQPR
ALSIIQGRAVGVAHYLLGGIATTWAFFLARIISVG

Sequence of entity 2 (aB, bB, cB), FASTA

>9LZJ_2 Photosystem I P700 chlorophyll a apoprotein A2 (chains aB, bB, cB)
MATKFPKFSQDLAQDPTTRRIWYAIAMAHDFESHDGMTEENLYQKIFASHFGHLAIIFLW
VSGSLFHVAWQGNFEQWVQDPVNTRPIAHAIWDPQFGKAAVDAFTQAGASNPVDIAYSGV
YHWWYTIGMRTNGDLYQGAIFLLILASLALFAGWLHLQPKFRPSLSWFKNAESRLNHHLA
GLFGVSSLAWAGHLIHVAIPESRGQHVGWDNFLSTMPHPAGLAPFFTGNWGVYAQNPDTA
SHVFGTAQGAGTAILTFLGGFHPQTESLWLTDMAHHHLAIAVLFIVAGHMYRTQFGIGHS
IKEMMDAKDFFGTKVEGPFNMPHQGIYETYNNSLHFQLGWHLACLGVITSLVAQHMYSLP
PYAFIAQDHTTMAALYTHHQYIAGFLMVGAFAHGAIFLVRDYDPAQNKGNVLDRVLQHKE
AIISHLSWVSLFLGFHTLGLYVHNDVVVAFGTPEKQILIEPVFAQFIQAAHGKLLYGFDT
LLSNPDSIASTAWPNYGNVWLPGWLDAINSGTNSLFLTIGPGDFLVHHAIALGLHTTTLI
LVKGALDARGSKLMPDKKDFGYAFPCDGPGRGGTCDISAWDAFYLAMFWMLNTIGWVTFY
WHWKHLGVWEGNVAQFNESSTYLMGWLRDYLWLNSSQLINGYNPFGTNNLSVWAWMFLFG
HLVWATGFMFLISWRGYWQELIETLVWAHERTPLANLVRWKDKPVALSIVQARLVGLAHF
SVGYILTYAAFLIASTAAKFG

Sequence of entity 3 (aC, bC, cC), FASTA

>9LZJ_3 Photosystem I iron-sulfur center (chains aC, bC, cC)
MAHTVKIYDTCIGCTQCVRACPTDVLEMVPWDGCKAGQIASSPRTEDCVGCKRCETACPT
DFLSIRVYLGAETTRSMGLAY

Sequence of entity 4 (aD, bD, cD), FASTA

>9LZJ_4 Photosystem I reaction center subunit II (chains aD, bD, cD)
MTTLTGQPPLYGGSTGGLLSAADTEEKYAITWTSPKEQVFEMPTAGAAVMREGENLVYFA
RKEQCLALAAQQLRPRKINDYKIYRIFPDGETVLIHPKDGVFPEKVNKGREAVNSVPRSI
GQNPNPSQLKFTGKKPYDP

Sequence of entity 5 (aE, bE, cE), FASTA

>9LZJ_5 Photosystem I reaction center subunit IV (chains aE, bE, cE)
MVQRGSKVKILRPESYWYNEVGTVASVDQTPGVKYPVIVRFDKVNYTGYSGSASGVNTNN
FALHEVQEVAPPKKGK

Sequence of entity 6 (aF, bF, cF), FASTA

>9LZJ_6 Photosystem I reaction center subunit III (chains aF, bF, cF)
MRRFLALLLVLTLWLGFTPLASADVAGLVPCKDSPAFQKRAAAAVNTTADPASGQKRFER
YSQALCGEDGLPHLVVDGRLSRAGDFLIPSVLFLYIAGWIGWVGRAYLIAVRNSGEANEK
EIIIDVPLAIKCMLTGFAWPLAALKELASGELTAKDNEITVSPR

Sequence of entity 7 (aI, bI, cI), FASTA

>9LZJ_7 Photosystem I reaction center subunit VIII (chains aI, bI, cI)
MMGSYAASFLPWIFIPVVCWLMPTVVMGLLFLYIEGEA

Sequence of entity 8 (aJ, bJ, cJ), FASTA

>9LZJ_8 Photosystem I reaction center subunit IX (chains aJ, bJ, cJ)
MKHFLTYLSTAPVLAAIWMTITAGILIEFNRFYPDLLFHPL

Sequence of entity 9 (aK, bK, cK), FASTA

>9LZJ_9 Photosystem I reaction center subunit PsaK (chains aK, bK, cK)
MVLATLPDTTWTPSVGLVVILCNLFAIALGRYAIQSRGKGPGLPIALPALFEGFGLPELL
ATTSFGHLLAAGVVSGLQYAGAL

Sequence of entity 10 (aL, bL, cL), FASTA

>9LZJ_10 Photosystem I reaction center subunit XI (chains aL, bL, cL)
MAEELVKPYNGDPFVGHLSTPISDSGLVKTFIGNLPAYRQGLSPILRGLEVGMAHGYFLI
GPWVKLGPLRDSDVANLGGLISGIALILVATACLAAYGLVSFQKGGSSSDPLKTSEGWSQ
FTAGFFVGAMGSAFVAFFLLENFSVVDGIMTGLFN

Sequence of entity 11 (aM, bM, cM), FASTA

>9LZJ_11 Photosystem I reaction center subunit XII (chains aM, bM, cM)
MALTDTQVYVALVIALLPAVLAFRLSTELYK

Sequence of entity 12 (aX, bX, cX), FASTA

>9LZJ_12 Photosystem I 4.8K protein (chains aX, bX, cX)
MSTMATKSAKPTYAFRTFWAVLLLAINFLVAAYYFGILK

Ligands and cofactors

ID	Name	Formula	Copies
CLA	Chlorophyll a	C55 H72 Mg N4 O5	1016
PQN	Phylloquinone	C31 H46 O2	6
SF4	Iron/sulfur cluster	Fe4 S4	9
BCR	Beta-carotene	C40 H56	238
LHG	1,2-dipalmitoyl-phosphatidyl-glycerole	C38 H75 O10 P	18
LMU	Dodecyl-alpha-D-maltoside	C24 H46 O11	12
SQD	1,2-di-O-acyl-3-O-[6-deoxy-6-sulfo-alpha-D-glucopyranosyl]-sn-glycerol	C41 H78 O12 S	40
LMG	1,2-distearoyl-monogalactosyl-diglyceride	C45 H86 O10	12
CA	Calcium ion	Ca	3

Primary citation

Structural basis for the assembly and energy transfer between the cyanobacterial PSI core and the double-layered IsiA proteins. Si, L., Zhang, Y., Su, X. et al. Nat Commun (2025) 17:592-592. DOI 10.1038/s41467-025-67295-2 · PubMed

Other PDB entries of the same protein (UniProt P0A405 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9QFP 1.74 Å, Monomeric Photosystem I Cryo-EM structure at 1.8 A resolution
7FIX 1.97 Å, Cryo-EM structure of cyanobacterial photosystem I in the presence of ferredoxin and…
1JB0 2.5 Å, Crystal Structure of Photosystem I: a Photosynthetic Reaction Center and Core Antenna…
7M75 2.75 Å, Room Temperature XFEL Crystallography reveals asymmetry in the vicinity of the two…
6TRA 2.85 Å, Cryo- EM structure of the Thermosynechococcus elongatus photosystem I in the presence of…
6PFY 2.9 Å, Membrane Protein Megahertz Crystallography at the European XFEL, Photosystem I at…
6PGK 2.9 Å, Membrane Protein Megahertz Crystallography at the European XFEL, Photosystem I XFEL at…
6TRC 2.98 Å, Cryo- EM structure of the Thermosynechococcus elongatus photosystem I in the presence of…
7M76 3.0 Å, Room Temperature XFEL Crystallography reveals asymmetry in the vicinity of the two…
7M78 3.0 Å, Room Temperature XFEL Crystallography reveals asymmetry in the vicinity of the two…
6TRD 3.16 Å, Cryo- EM structure of the Thermosynechococcus elongatus photosystem I in the presence of…
6LU1 3.2 Å, Cyanobacterial PSI Monomer from T. elongatus by Single Particle CRYO-EM at 3.2 A…

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