9LZK: Iron stress-induced chlorophyll-binding protein
The PSI1-IsiA13 complex with double-layered IsiA proteins bound to the monomeric PSI core. Determined by electron microscopy at 3.5 Å resolution. Released 31 Dec 2025.
- Method
- Electron microscopy
- Resolution
- 3.5 Å
- Organism
- Thermosynechococcus vestitus BP-1
- Chains
- 24
- Atoms
- 72,827
- Mol. weight
- 1095.13 kDa
- Ligands
- CLA, BCR, SQD, LMG
- Released
- 31 Dec 2025
Explore 9LZK in 3D
Show helices and sheets
RCSB PDB
PDBe
Secondary structure: helices and β-sheets
9LZK contains 332 α-helices and 134 β-strands across 24 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 1: 17 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 | 94 | 1 | 16 |
| α-helix | 102-123 | 22 | |
| α-helix | 124-128 | 5 | |
| α-helix | 139-142 | 4 | |
| α-helix | 150-176 | 27 | |
| β-strand | 181-182 | 2 | 17 |
| β-strand | 188 | 1 | 16 |
| β-strand | 189-190 | 2 | 17 |
| α-helix | 199-203 | 5 | |
| α-helix | 204-206 | 3 | |
| α-helix | 215-238 | 24 | |
| α-helix | 240-242 | 3 | |
| α-helix | 243-246 | 4 | |
| α-helix | 253-277 | 25 | |
| α-helix | 290-291 | 2 | |
| β-strand | 292 | 1 | 18 |
| β-strand | 302 | 1 | 18 |
| α-helix | 308-310 | 3 | |
| α-helix | 314-341 | 28 | |
| α-helix | 346-351 | 6 | |
Chain 2: 18 helices, 6 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-36 | 9 | |
| α-helix | 39-67 | 29 | |
| α-helix | 81-87 | 7 | |
| β-strand | 92 | 1 | 13 |
| α-helix | 94-96 | 3 | |
| β-strand | 98 | 1 | 13 |
| 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 | 14 |
| β-strand | 188-190 | 3 | 14 |
| α-helix | 199-203 | 5 | |
| α-helix | 204-206 | 3 | |
| α-helix | 215-238 | 24 | |
| 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 | 15 |
| β-strand | 299-302 | 4 | 15 |
| α-helix | 308-310 | 3 | |
| α-helix | 314-341 | 28 | |
| α-helix | 345-350 | 6 | |
Chain 3: 18 helices, 6 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-36 | 9 | |
| α-helix | 39-66 | 28 | |
| α-helix | 81-88 | 8 | |
| β-strand | 92 | 1 | 1 |
| α-helix | 94-96 | 3 | |
| β-strand | 98 | 1 | 1 |
| α-helix | 102-127 | 26 | |
| α-helix | 139-142 | 4 | |
| α-helix | 150-176 | 27 | |
| β-strand | 181-183 | 3 | 2 |
| β-strand | 188-190 | 3 | 2 |
| 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 | 3 |
| β-strand | 299-302 | 4 | 3 |
| α-helix | 308-310 | 3 | |
| α-helix | 314-341 | 28 | |
| α-helix | 346-352 | 7 | |
Chain 4: 17 helices, 6 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-35 | 8 | |
| α-helix | 39-67 | 29 | |
| α-helix | 82-87 | 6 | |
| β-strand | 92-93 | 2 | 4 |
| β-strand | 97-98 | 2 | 4 |
| α-helix | 102-127 | 26 | |
| α-helix | 139-142 | 4 | |
| α-helix | 150-176 | 27 | |
| β-strand | 181-183 | 3 | 5 |
| β-strand | 188-190 | 3 | 5 |
| α-helix | 201-204 | 4 | |
| α-helix | 215-238 | 24 | |
| α-helix | 240-242 | 3 | |
| α-helix | 243-246 | 4 | |
| α-helix | 253-277 | 25 | |
| α-helix | 284-287 | 4 | |
| α-helix | 290-291 | 2 | |
| β-strand | 292-295 | 4 | 6 |
| β-strand | 299-302 | 4 | 6 |
| α-helix | 308-310 | 3 | |
| α-helix | 314-341 | 28 | |
| α-helix | 345-348 | 4 | |
| α-helix | 349-352 | 4 | |
Chain 5: 14 helices, 7 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-35 | 8 | |
| α-helix | 39-67 | 29 | |
| α-helix | 81-88 | 8 | |
| β-strand | 92 | 1 | 7 |
| β-strand | 94 | 1 | 8 |
| β-strand | 98 | 1 | 7 |
| 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 | 8 |
| β-strand | 188-190 | 3 | 8 |
| α-helix | 199-204 | 6 | |
| α-helix | 215-238 | 24 | |
| 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 | 9 |
| β-strand | 299-302 | 4 | 9 |
| α-helix | 314-341 | 28 | |
Chain 6: 16 helices, 6 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-36 | 9 | |
| α-helix | 39-67 | 29 | |
| α-helix | 82-88 | 7 | |
| β-strand | 92-94 | 3 | 10 |
| β-strand | 97-98 | 2 | 10 |
| α-helix | 102-123 | 22 | |
| α-helix | 124-128 | 5 | |
| α-helix | 133-135 | 3 | |
| α-helix | 139-143 | 5 | |
| α-helix | 150-176 | 27 | |
| β-strand | 182-183 | 2 | 11 |
| β-strand | 188-189 | 2 | 11 |
| α-helix | 199-203 | 5 | |
| α-helix | 204-207 | 4 | |
| α-helix | 216-238 | 23 | |
| α-helix | 243-248 | 6 | |
| α-helix | 253-277 | 25 | |
| α-helix | 290-291 | 2 | |
| β-strand | 292-295 | 4 | 12 |
| β-strand | 299-302 | 4 | 12 |
| α-helix | 314-340 | 27 | |
| α-helix | 345-350 | 6 | |
Chain a: 17 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 28-35 | 8 | |
| α-helix | 39-67 | 29 | |
| α-helix | 82-86 | 5 | |
| α-helix | 102-127 | 26 | |
| α-helix | 139-143 | 5 | |
| α-helix | 150-176 | 27 | |
| β-strand | 181-183 | 3 | 59 |
| β-strand | 188-190 | 3 | 59 |
| α-helix | 199-207 | 9 | |
| α-helix | 215-238 | 24 | |
| α-helix | 240-242 | 3 | |
| α-helix | 243-248 | 6 | |
| α-helix | 250-251 | 2 | |
| α-helix | 253-277 | 25 | |
| α-helix | 284-287 | 4 | |
| β-strand | 292-295 | 4 | 60 |
| β-strand | 299-302 | 4 | 60 |
| α-helix | 308-310 | 3 | |
| α-helix | 311-313 | 3 | |
| α-helix | 314-340 | 27 | |
| α-helix | 345-352 | 8 | |
Chain A: 47 helices, 19 β-strands
| Element | Residues | Length | Sheet |
|---|
| β-strand | 16-18 | 3 | 19 |
| α-helix | 37-40 | 4 | |
| β-strand | 44 | 1 | 20 |
| α-helix | 46-53 | 8 | |
| α-helix | 58-61 | 4 | |
| α-helix | 65-95 | 31 | |
| β-strand | 98 | 1 | 21 |
| α-helix | 100-105 | 6 | |
| α-helix | 111-112 | 2 | |
| β-strand | 113-114 | 2 | 21 |
| α-helix | 123-126 | 4 | |
| β-strand | 128-129 | 2 | 22 |
| β-strand | 135-136 | 2 | 22 |
| β-strand | 137-138 | 2 | 21 |
| α-helix | 143-150 | 8 | |
| α-helix | 155-177 | 23 | |
| α-helix | 178-182 | 5 | |
| β-strand | 183-185 | 3 | 19 |
| 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 | 233-235 | 3 | |
| 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 | |
| β-strand | 285 | 1 | 23 |
| β-strand | 292 | 1 | 23 |
| α-helix | 294-312 | 19 | |
| β-strand | 315 | 1 | 24 |
| β-strand | 323 | 1 | 24 |
| α-helix | 325-331 | 7 | |
| α-helix | 344-350 | 7 | |
| 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 | 485-495 | 11 | |
| β-strand | 498 | 1 | 25 |
| β-strand | 502 | 1 | 25 |
| β-strand | 518-520 | 3 | 26 |
| β-strand | 523-526 | 4 | 26 |
| α-helix | 533-558 | 26 | |
| α-helix | 569-572 | 4 | |
| α-helix | 591-616 | 26 | |
| α-helix | 617-621 | 5 | |
| β-strand | 623-625 | 3 | 26 |
| β-strand | 631-633 | 3 | 26 |
| 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 | 20 |
| α-helix | 719 | 1 | |
| α-helix | 721-723 | 3 | |
| α-helix | 724-754 | 31 | |
16 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 |
|---|
| Iron stress-induced chlorophyll-binding protein | 1, 2, 3, 4, 5, 6, a, b, c, d, e, f, g | protein | 358 | Thermosynechococcus vestitus BP-1 | Q8DK20 (AlphaFold model) |
| Photosystem I P700 chlorophyll a apoprotein A1 | A | protein | 755 | Thermosynechococcus vestitus BP-1 | P0A405 (AlphaFold model) |
| Photosystem I P700 chlorophyll a apoprotein A2 | B | protein | 741 | Thermosynechococcus vestitus BP-1 | P0A407 (AlphaFold model) |
| Photosystem I iron-sulfur center | C | protein | 81 | Thermosynechococcus vestitus BP-1 | P0A415 (AlphaFold model) |
| Photosystem I reaction center subunit II | D | protein | 139 | Thermosynechococcus vestitus BP-1 | P0A420 |
| Photosystem I reaction center subunit IV | E | protein | 76 | Thermosynechococcus vestitus BP-1 | P0A423 |
| Photosystem I reaction center subunit III | F | protein | 164 | Thermosynechococcus vestitus BP-1 | P0A401 |
| Photosystem I reaction center subunit VIII | I | protein | 38 | Thermosynechococcus vestitus BP-1 | P0A427 |
| Photosystem I reaction center subunit IX | J | protein | 41 | Thermosynechococcus vestitus BP-1 | P0A429 |
| Photosystem I reaction center subunit PsaK | K | protein | 83 | Thermosynechococcus vestitus BP-1 | P0A425 |
| Photosystem I reaction center subunit XII | M | protein | 31 | Thermosynechococcus vestitus BP-1 | P0A403 |
| Photosystem I 4.8K protein | X | protein | 39 | Thermosynechococcus vestitus BP-1 | Q8DKP6 |
Sequence of entity 1 (1, 2, 3, 4, 5, 6, a, b, c, d, e, f, g), FASTA
>9LZK_1 Iron stress-induced chlorophyll-binding protein (chains 1, 2, 3, 4, 5, 6, a, b, c, d, e, f, g)
MAIASESPTTVTSAGLQTYGQTNVKYDWWAGNARFVNLSGLFIAAHVAQAALSVFWAGAF
TLYEISQYKPDLPMGEQGLILLPHLATLGFGIGEGGKVVDLYPYFVIGAVHLISSAVLGA
GALFHTFRAPHDLSTATGRARRFHFRWDDPKQLGIILGHHLLFLGFGALLLVLKATIWGG
LYDANLQTVRLITQPTLDPFVIYGYQTHFASINSLEDLVGGHIYIAILLIAGGIWHILVP
PLTWARKLLMFNAEAILSYSLGGIALAGFVAAYFCAVNTLAYPVEFYGPPLEVKLGIAPY
FADTIELPLGQHTSRAWLANAHFFLAFFFLQGHLWHALRAMGFNFKQLETFLNPAIEN
Sequence of entity 2 (A), FASTA
>9LZK_2 Photosystem I P700 chlorophyll a apoprotein A1 (chains A)
MTISPPEREPKVRVVVDNDPVPTSFEKWAKPGHFDRTLARGPQTTTWIWNLHALAHDFDT
HTSDLEDISRKIFSAHFGHLAVVFIWLSGMYFHGAKFSNYEAWLADPTGIKPSAQVVWPI
VGQGILNGDVGGGFHGIQITSGLFQLWRASGITNEFQLYCTAIGGLVMAGLMLFAGWFHY
HKRAPKLEWFQNVESMLNHHLAGLLGLGSLAWAGHQIHVSLPINKLLDAGVAAKDIPLPH
EFILNPSLMAELYPKVDWGFFSGVIPFFTFNWAAYSDFLTFNGGLNPVTGGLWLSDTAHH
HLAIAVLFIIAGHMYRTNWGIGHSLKEILEAHKGPFTGAGHKGLYEVLTTSWHAQLAINL
AMMGSLSIIVAQHMYAMPPYPYLATDYPTQLSLFTHHMWIGGFLVVGGAAHGAIFMVRDY
DPAMNQNNVLDRVLRHRDAIISHLNWVCIFLGFHSFGLYVHNDTMRAFGRPQDMFSDTGI
QLQPVFAQWVQNLHTLAPGGTAPNAAATASVAFGGDVVAVGGKVAMMPIVLGTADFMVHH
IHAFTIHVTVLILLKGVLFARSSRLIPDKANLGFRFPCDGPGRGGTCQVSGWDHVFLGLF
WMYNCISVVIFHFSWKMQSDVWGTVAPDGTVSHITGGNFAQSAITINGWLRDFLWAQASQ
VIGSYGSALSAYGLLFLGAHFIWAFSLMFLFSGRGYWQELIESIVWAHNKLKVAPAIQPR
ALSIIQGRAVGVAHYLLGGIATTWAFFLARIISVG
Sequence of entity 3 (B), FASTA
>9LZK_3 Photosystem I P700 chlorophyll a apoprotein A2 (chains B)
MATKFPKFSQDLAQDPTTRRIWYAIAMAHDFESHDGMTEENLYQKIFASHFGHLAIIFLW
VSGSLFHVAWQGNFEQWVQDPVNTRPIAHAIWDPQFGKAAVDAFTQAGASNPVDIAYSGV
YHWWYTIGMRTNGDLYQGAIFLLILASLALFAGWLHLQPKFRPSLSWFKNAESRLNHHLA
GLFGVSSLAWAGHLIHVAIPESRGQHVGWDNFLSTMPHPAGLAPFFTGNWGVYAQNPDTA
SHVFGTAQGAGTAILTFLGGFHPQTESLWLTDMAHHHLAIAVLFIVAGHMYRTQFGIGHS
IKEMMDAKDFFGTKVEGPFNMPHQGIYETYNNSLHFQLGWHLACLGVITSLVAQHMYSLP
PYAFIAQDHTTMAALYTHHQYIAGFLMVGAFAHGAIFLVRDYDPAQNKGNVLDRVLQHKE
AIISHLSWVSLFLGFHTLGLYVHNDVVVAFGTPEKQILIEPVFAQFIQAAHGKLLYGFDT
LLSNPDSIASTAWPNYGNVWLPGWLDAINSGTNSLFLTIGPGDFLVHHAIALGLHTTTLI
LVKGALDARGSKLMPDKKDFGYAFPCDGPGRGGTCDISAWDAFYLAMFWMLNTIGWVTFY
WHWKHLGVWEGNVAQFNESSTYLMGWLRDYLWLNSSQLINGYNPFGTNNLSVWAWMFLFG
HLVWATGFMFLISWRGYWQELIETLVWAHERTPLANLVRWKDKPVALSIVQARLVGLAHF
SVGYILTYAAFLIASTAAKFG
Sequence of entity 4 (C), FASTA
>9LZK_4 Photosystem I iron-sulfur center (chains C)
MAHTVKIYDTCIGCTQCVRACPTDVLEMVPWDGCKAGQIASSPRTEDCVGCKRCETACPT
DFLSIRVYLGAETTRSMGLAY
Sequence of entity 5 (D), FASTA
>9LZK_5 Photosystem I reaction center subunit II (chains D)
MTTLTGQPPLYGGSTGGLLSAADTEEKYAITWTSPKEQVFEMPTAGAAVMREGENLVYFA
RKEQCLALAAQQLRPRKINDYKIYRIFPDGETVLIHPKDGVFPEKVNKGREAVNSVPRSI
GQNPNPSQLKFTGKKPYDP
Sequence of entity 6 (E), FASTA
>9LZK_6 Photosystem I reaction center subunit IV (chains E)
MVQRGSKVKILRPESYWYNEVGTVASVDQTPGVKYPVIVRFDKVNYTGYSGSASGVNTNN
FALHEVQEVAPPKKGK
Sequence of entity 7 (F), FASTA
>9LZK_7 Photosystem I reaction center subunit III (chains F)
MRRFLALLLVLTLWLGFTPLASADVAGLVPCKDSPAFQKRAAAAVNTTADPASGQKRFER
YSQALCGEDGLPHLVVDGRLSRAGDFLIPSVLFLYIAGWIGWVGRAYLIAVRNSGEANEK
EIIIDVPLAIKCMLTGFAWPLAALKELASGELTAKDNEITVSPR
Sequence of entity 8 (I), FASTA
>9LZK_8 Photosystem I reaction center subunit VIII (chains I)
MMGSYAASFLPWIFIPVVCWLMPTVVMGLLFLYIEGEA
Sequence of entity 9 (J), FASTA
>9LZK_9 Photosystem I reaction center subunit IX (chains J)
MKHFLTYLSTAPVLAAIWMTITAGILIEFNRFYPDLLFHPL
Sequence of entity 10 (K), FASTA
>9LZK_10 Photosystem I reaction center subunit PsaK (chains K)
MVLATLPDTTWTPSVGLVVILCNLFAIALGRYAIQSRGKGPGLPIALPALFEGFGLPELL
ATTSFGHLLAAGVVSGLQYAGAL
Sequence of entity 11 (M), FASTA
>9LZK_11 Photosystem I reaction center subunit XII (chains M)
MALTDTQVYVALVIALLPAVLAFRLSTELYK
Sequence of entity 12 (X), FASTA
>9LZK_12 Photosystem I 4.8K protein (chains X)
MSTMATKSAKPTYAFRTFWAVLLLAINFLVAAYYFGILK
Ligands and cofactors
| ID | Name | Formula | Copies |
|---|
| CLA | Chlorophyll a | C55 H72 Mg N4 O5 | 313 |
| BCR | Beta-carotene | C40 H56 | 73 |
| SQD | 1,2-di-O-acyl-3-O-[6-deoxy-6-sulfo-alpha-D-glucopyranosyl]-sn-glycerol | C41 H78 O12 S | 14 |
| LMG | 1,2-distearoyl-monogalactosyl-diglyceride | C45 H86 O10 | 6 |
| LHG | 1,2-dipalmitoyl-phosphatidyl-glycerole | C38 H75 O10 P | 5 |
| PQN | Phylloquinone | C31 H46 O2 | 2 |
| SF4 | Iron/sulfur cluster | Fe4 S4 | 3 |
| LMU | Dodecyl-alpha-D-maltoside | C24 H46 O11 | 4 |
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 Q8DK20 (AlphaFold model), which also has an AlphaFold model), best resolution first:
- 9LZJ 3.4 Å, The PSI3-IsiA43 complex with a closed double ring of IsiA proteins bound to a trimeric…
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