9PQK: Maltose/maltodextrin-binding periplasmic protein

Crystal structure of maltose binding protein (Apo), mutant Trp10 to 4-Fluorotryptophan. Determined by X-ray diffraction at 1.87 Å resolution. Released 5 Aug 2026.

Method: X-ray diffraction
Resolution: 1.87 Å
Organism: Escherichia coli
Chains: 1
Atoms: 3,028
Mol. weight: 41.38 kDa
Ligands: CD
Released: 5 Aug 2026

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

Secondary structure: helices and β-sheets

9PQK contains 24 α-helices and 24 β-strands across 1 chain. 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: 24 helices, 24 β-strands

Element	Residues	Length	Sheet
α-helix	2-3	2
β-strand	6-10	5	1
α-helix	17-31	15
β-strand	34-38	5	1
α-helix	43-51	9
β-strand	59-63	5	1
α-helix	64-66	3
α-helix	67-72	6
β-strand	76	1	2
α-helix	77-79	3
α-helix	83-87	5
β-strand	89	1	3
α-helix	91-95	5
β-strand	98-99	2	4
β-strand	102-103	2	4
β-strand	106-111	6	1
β-strand	114-118	5	5
β-strand	128	1	6
α-helix	129-131	3
α-helix	132-140	9
β-strand	145-147	3	5
α-helix	154-161	8
β-strand	167-172	6	7
β-strand	175-182	8	7
α-helix	186-200	15
α-helix	210-218	9
β-strand	222-227	6	5
α-helix	229-234	6
β-strand	242-245	4	5
α-helix	246-248	3
β-strand	249	1	6
β-strand	250	1	8
β-strand	253	1	8
α-helix	254-255	2
β-strand	258-259	2	9
β-strand	260-266	7	1
β-strand	267	1	2
α-helix	273-279	7
α-helix	280-284	5
α-helix	287-296	10
β-strand	301-302	2	1
β-strand	304	1	3
α-helix	305-311	7
α-helix	315-326	12
β-strand	328-329	2	9
α-helix	330-331	2
α-helix	336-352	17
α-helix	357-369	13

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Maltose/maltodextrin-binding periplasmic protein	A	protein	370	Escherichia coli	P0AEY0 (AlphaFold model)

Sequence of entity 1 (A), FASTA

>9PQK_1 Maltose/maltodextrin-binding periplasmic protein (chains A)
KIEEGKLVIWINGDKGYNGLAEVGKKFEKDTGIKVTVEHPDKLEEKFPQVAATGDGPDII
FWAHDRFGGYAQSGLLAEITPDKAFQDKLYPFTWDAVRYNGKLIAYPIAVEALSLIYNKD
LLPNPPKTWEEIPALDKELKAKGKSALMFNLQEPYFTWPLIAADGGYAFKYENGKYDIKD
VGVDNAGAKAGLTFLVDLIKNKHMNADTDYSIAEAAFNKGETAMTINGPWAWSNIDTSKV
NYGVTVLPTFKGQPSKPFVGVLSAGINAASPNKELAKEFLENYLLTDEGLEAVNKDKPLG
AVALKSYEEELAKDPRIAATMENAQKGEIMPNIPQMSAFWYAVRTAVINAASGRQAVDEA
LKDAQTRITK

Ligands and cofactors

ID	Name	Formula	Copies
CD	Cadmium ion	Cd	4

Water and common crystallization additives (NA, EDO) are not listed.

Primary citation

Structural accomodations of tryptophan 4-substitutions in maltose binding protein. Habel, E., Huber, T. To be published.

Other PDB entries of the same protein (UniProt P0AEY0 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9PQP 1.07 Å, Crystal structure of maltose binding protein (Apo), mutant Trp340 to 4-Fluorotryptophan
9PQL 1.37 Å, Crystal structure of maltose binding protein (Apo), mutant Trp62 to 4-Fluorotryptophan
9PQN 1.37 Å, Crystal structure of maltose binding protein (Apo), mutant Trp340 to 4-Cyanotryptophan
9TY2 1.75 Å, Crystal structure of a Picomolar Nanobody in complex with Maltose Binding Protein, MBP,…
4WGI 1.85 Å, A Single Diastereomer of a Macrolactam Core Binds Specifically to Myeloid Cell Leukemia…
4WVI 1.9 Å, Crystal structure of the Type-I signal peptidase from Staphylococcus aureus (SpsB) in…
4WVJ 1.95 Å, Crystal structure of the Type-I signal peptidase from Staphylococcus aureus (SpsB) in…
4YS9 2.0 Å, Ataxin-3 Carboxy-Terminal Region - Crystal C1 (tetragonal)
5II4 2.0 Å, Crystal structure of red abalone VERL repeat 1 with linker at 2.0 A resolution
5JON 2.04 Å, Crystal structure of the unliganded form of HCN2 CNBD
4WVG 2.05 Å, Crystal structure of the Type-I signal peptidase from Staphylococcus aureus (SpsB).
3VD8 2.07 Å, Crystal structure of human AIM2 PYD domain with MBP fusion

Browse structure collections

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