9SKR: PDB entry 9SKR

Cryo-EM structure of H. neapolitanus CsoSCA in oxidizing conditions, hexamer. Determined by electron microscopy at 2.13 Å resolution. Released 22 Apr 2026.

Method: Electron microscopy
Resolution: 2.13 Å
Organisms: Escherichia coli K-12, Halothiobacillus neapolitanus c2
Chains: 2
Atoms: 7,703
Mol. weight: 204.22 kDa
Ligands: ZN
Released: 22 Apr 2026

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

Secondary structure: helices and β-sheets

9SKR contains 49 α-helices and 26 β-strands across 2 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, 13 β-strands

Element	Residues	Length	Sheet
α-helix	56-74	19
α-helix	76-84	9
α-helix	92-104	13
α-helix	110-113	4
α-helix	116-119	4
α-helix	123-148	26
α-helix	153-162	10
β-strand	165-172	8	1
β-strand	173	1	2
α-helix	176-178	3
α-helix	181-186	6
α-helix	188-190	3
β-strand	194-196	3	1
β-strand	199	1	2
α-helix	200-202	3
α-helix	206-223	18
β-strand	234-243	10	1
α-helix	260-281	22
β-strand	288-296	9	1
β-strand	301-305	5	1
α-helix	306-307	2
β-strand	318-320	3	1
α-helix	321-328	8
α-helix	333-348	16
α-helix	352-354	3
α-helix	363-386	24
α-helix	392-394	3
β-strand	401-405	5	3
β-strand	417-420	4	3
α-helix	426-428	3
α-helix	429-442	14
α-helix	444-446	3
β-strand	450-458	9	3
α-helix	465-483	19
α-helix	485-488	4
β-strand	493-501	9	3
α-helix	506-507	2
β-strand	508-511	4	3

Chain B: 24 helices, 13 β-strands

Element	Residues	Length	Sheet
α-helix	56-74	19
α-helix	76-83	8
α-helix	92-104	13
α-helix	110-113	4
α-helix	116-119	4
α-helix	123-144	22
α-helix	152-162	11
β-strand	165-172	8	4
β-strand	173	1	5
α-helix	176-178	3
α-helix	181-186	6
α-helix	188-190	3
β-strand	194-196	3	4
β-strand	199	1	5
α-helix	200-202	3
α-helix	206-223	18
β-strand	234-243	10	4
α-helix	260-281	22
β-strand	288-296	9	4
β-strand	301-305	5	4
α-helix	306-307	2
β-strand	318-320	3	4
α-helix	321-328	8
α-helix	333-349	17
α-helix	362-386	25
α-helix	392-394	3
β-strand	401-405	5	6
β-strand	417-420	4	6
α-helix	426-428	3
α-helix	429-442	14
α-helix	444-446	3
β-strand	450-458	9	6
α-helix	465-483	19
α-helix	485-488	4
β-strand	493-501	9	6
α-helix	506-507	2
β-strand	508-511	4	6

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Maltose/maltodextrin-binding periplasmic protein,Carboxysome shell carbonic anhydrase	A, B	protein	919	Escherichia coli K-12, Halothiobacillus neapolitanus c2	O85042 (AlphaFold model), P0AEX9 (AlphaFold model)

Sequence of entity 1 (A, B), FASTA

>9SKR_1 Maltose/maltodextrin-binding periplasmic protein,Carboxysome shell carbonic anhydrase (chains A, B)
MWSHPQFEKGSSMKIEEGKLVIWINGDKGYNGLAEVGKKFEKDTGIKVTVEHPDKLEEKF
PQVAATGDGPDIIFWAHDRFGGYAQSGLLAEITPDKAFQDKLYPFTWDAVRYNGKLIAYP
IAVEALSLIYNKDLLPNPPKTWEEIPALDKELKAKGKSALMFNLQEPYFTWPLIAADGGY
AFKYENGKYDIKDVGVDNAGAKAGLTFLVDLIKNKHMNADTDYSIAEAAFNKGETAMTIN
GPWAWSNIDTSKVNYGVTVLPTFKGQPSKPFVGVLSAGINAASPNKELAKEFLENYLLTD
EGLEAVNKDKPLGAVALKSYEEELAKDPRIAATMENAQKGEIMPNIPQMSAFWYAVRTAV
INAASGRQTVDEALKDAQTNSSSNNNNNNNNNNLGIEENLYFQSNANTRNTRSKQRAPFG
VSSSVKPRLDLIEQAPNPAYDRHPACITLPERTCRHPLTDLEANEQLGRCEDSVKNRFDR
VIPFLQVVAGIPLGLDYVTRVQELAQSSLGHTLPEELLKDNWISGHNLKGIFGYATAKAL
TAATEQFSRKIMSEKDDSASAIGFFLDCGFHAVDISPCADGRLKGLLPYILRLPLTAFTY
RKAYAGSMFDIEDDLAQWEKNELRRYREGVPNTADQPTRYLKIAVYHFSTSDPTHSGCAA
HGSNDRAALEAALTQLMKFREAVENAHCCGASIDILLIGVDTDTDAIRVHIPDSKGFLNP
YRYVDNTVTYAQTLHLAPDEARVIIHEAILNANRSDGWAKGNGVASEGMRRFIGQLLINN
LSQIDYVVNRHGGRYPPNDIGHAERYISVGDGFDEVQIRNLAYYAHLDTVEENAIDVDVG
IKIFTKLNLSRGLPIPIAIHYRYDPNVPGSRERTVVKARRIYNAIKERFSSLDEQNLLQF
RLSVQAQDIGSPIEEVASA

Ligands and cofactors

ID	Name	Formula	Copies
ZN	Zinc ion	Zn	2

Primary citation

Molecular mechanism of redox regulation of the alpha-carboxysomal carbonic anhydrase CsoSCA. Vogiatzi, N., Gaullier, G., Leufstadius, J. et al. bioRxiv (2026). DOI 10.64898/2026.04.02.716132

Other PDB entries of the same protein (UniProt O85042 (AlphaFold model), which also has an AlphaFold model), best resolution first:

7SMK 1.98 Å, H. neapolitanus carboxysomal rubisco/CsoSCA-peptide (1-50)complex
9SKU 2.06 Å, Cryo-EM structure of H. neapolitanus CsoSCA in reducing conditions, hexamer
7SNV 2.07 Å, H. neapolitanus carboxysomal rubisco/CsoSCA-peptide (1-50)complex
9SKX 2.08 Å, Cryo-EM structure of H. neapolitanus CsoSCA C283A/C284A inactive mutant, hexamer
9SKV 2.12 Å, Cryo-EM structure of H. neapolitanus CsoSCA in reducing conditions, dimer, major state,…
9SKS 2.15 Å, Cryo-EM structure of H. neapolitanus CsoSCA in oxidizing conditions, dimer, major state,…
9SKY 2.18 Å, Cryo-EM structure of H. neapolitanus CsoSCA C283A/C284A inactive mutant, dimer, state 1
2FGY 2.2 Å, Beta Carbonic Anhydrase from the Carboxysomal Shell of Halothiobacillus neapolitanus…
9SKZ 2.22 Å, Cryo-EM structure of H. neapolitanus CsoSCA C283A/C284A inactive mutant, dimer, state 2
9SKW 2.27 Å, Cryo-EM structure of H. neapolitanus CsoSCA in reducing conditions, dimer, minor state
9SKT 2.45 Å, Cryo-EM structure of H. neapolitanus CsoSCA in oxidizing conditions, dimer, minor state
9G4T 2.51 Å, Beta carbonic anhydrase CsoSCA from the Halothiobacillus neapolitanus alpha-carboxysome

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