9KQ0: TolQRA complex at pH 8.0 from E.coli

Structure of TolQRA complex at pH 8.0 from E.coli. Determined by electron microscopy at 3.6 Å resolution. Released 4 Mar 2026.

Method: Electron microscopy
Resolution: 3.6 Å
Organisms: Escherichia coli K-12, Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
Chains: 12
Atoms: 10,048
Mol. weight: 452.16 kDa
Released: 4 Mar 2026

Explore 9KQ0 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9KQ0 contains 47 α-helices and 0 β-strands across 12 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: 7 helices, 0 β-strands

Element	Residues	Length
α-helix	6-12	7
α-helix	15-56	42
α-helix	62-72	11
α-helix	78-96	19
α-helix	101-123	23
α-helix	127-157	31
α-helix	168-229	62

Chain B: 7 helices, 0 β-strands

Element	Residues	Length
α-helix	6-11	6
α-helix	15-56	42
α-helix	62-71	10
α-helix	79-96	18
α-helix	101-123	23
α-helix	127-157	31
α-helix	168-221	54

Chain C: 9 helices, 0 β-strands

Element	Residues	Length
α-helix	6-12	7
α-helix	15-57	43
α-helix	62-72	11
α-helix	73-75	3
α-helix	78-96	19
α-helix	101-123	23
α-helix	127-156	30
α-helix	164-189	26
α-helix	192-224	33

Chain D: 8 helices, 0 β-strands

Element	Residues	Length
α-helix	8-11	4
α-helix	16-56	41
α-helix	62-71	10
α-helix	73-75	3
α-helix	79-96	18
α-helix	104-123	20
α-helix	127-158	32
α-helix	168-219	52

Chain E: 9 helices, 0 β-strands

Element	Residues	Length
α-helix	6-11	6
α-helix	15-56	42
α-helix	62-71	10
α-helix	73-75	3
α-helix	79-97	19
α-helix	101-124	24
α-helix	127-133	7
α-helix	137-157	21
α-helix	164-223	60

Chain F: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	21-32	12

Chain G: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	18-34	17

Chains H and L: 1 helix, 0 β-strands

Element	Residues	Length	Sheet
α-helix	9-34	26

3 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
Tol-Pal system protein TolQ	A, B, C, D, E	protein	232	Escherichia coli K-12	P0ABU9 (AlphaFold model)
Tol-Pal system protein TolR	F, G	protein	142	Escherichia coli K-12	P0ABV6 (AlphaFold model)
Ubiquitin-like protein SMT3,Tol-Pal system protein TolA	H, I, J, K, L	protein	557	Saccharomyces cerevisiae (strain ATCC 204508 / S288c), Escherichia coli K-12	P19934 (AlphaFold model), Q12306 (AlphaFold model)

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

>9KQ0_1 Tol-Pal system protein TolQ (chains A, B, C, D, E)
MGVTDMNILDLFLKASLLVKLIMLILIGFSIASWAIIIQRTRILNAAAREAEAFEDKFWS
GIELSRLYQESQGKRDNLTGSEQIFYSGFKEFVRLHRANSHAPEAVVEGASRAMRISMNR
ELENLETHIPFLGTVGSISPYIGLFGTVWGIMHAFIALGAVKQATLQMVAPGIAEALIAT
AIGLFAAIPAVMAYNRLNQRVNKLELNYDNFMEEFTAILHRQAFTVSESNKG

Sequence of entity 2 (F, G), FASTA

>9KQ0_2 Tol-Pal system protein TolR (chains F, G)
MARARGRGRRDLKSEINIVPLLDVLLVLLLIFMATAPIITQSVEVDLPDATESQAVSSND
NPPVIVEVSGIGQYTVVVEKDRLERLPPEQVVAEVSSRFKANPKTVFLIGGAKDVPYDEI
IKALNLLHSAGVKSVGLMTQPI

Sequence of entity 3 (H, I, J, K, L), FASTA

>9KQ0_3 Ubiquitin-like protein SMT3,Tol-Pal system protein TolA (chains H, I, J, K, L)
MGHHHHHHHHGSLQDSEVNQEAKPEVKPEVKPETHINLKVSDGSSEIFFKIKKTTPLRRL
MEAFAKRQGKEMDSLRFLYDGIRIQADQTPEDLDMEDNDIIEAHREQIGGAAADYGGDIP
TTENLYFQGAAADIGSVSKATEQNDKLKRAIIISAVLHVILFAALIWSSFDENIEASAGG
GGGSSIDAVMVDSGAVVEQYKRMQSQESSAKRSDEQRKMKEQQAAEELREKQAAEQERLK
QLEKERLAAQEQKKQAEEAAKQAELKQKQAEEAAAKAAADAKAKAEADAKAAEEAAKKAA
ADAKKKAEAEAAKAAAEAQKKAEAAAAALKKKAEAAEAAAAEARKKAATEAAEKAKAEAE
KKAAAEKAAADKKAAAEKAAADKKAAEKAAAEKAAADKKAAAEKAAADKKAAAAKAAAEK
AAAAKAAAEADDIFGELSSGKNAPKTGGGAKGNNASPAGSGNTKNNGASGADINNYAGQI
KSAIESKFYDASSYAGKTCTLRIKLAPDGMLLDIKPEGGDPALCQAALAAAKLAKIPKPP
SQAVYEVFKNAPLDFKP

Primary citation

Structure of TolQRA complex at pH 8.0 from E.coli. Dong, C., Zhang, Z. To be published.

Other PDB entries of the same protein (UniProt P0ABU9 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9O40 2.92 Å, cryo-EM structure of TolQR conformation1 in SMA nanodiscs
9DDM 2.94 Å, E. coli TolAQR conformation I
9DDN 3.18 Å, E. coli TolAQR conformation II
9KPZ 3.18 Å, Structure of TolQRA complex at pH 5.4 from E.coli
9QUQ 3.28 Å, cryo-EM structure of TolQR conformation2 in SMA nanodiscs
9QVD 3.52 Å, cryo-EM structure of TolQRA in nanodiscs
9K49 3.6 Å, Cryo-EM structure of inner membrane TolQRA complex in CYMAL-6-Neopentyl Glycol detergent…
9KCH 4.19 Å, Cryo-EM structure of inner membrane TolQRA complex in CYMAL-6-Neopentyl Glycol detergent…
8ODT 4.2 Å, Structure of TolQR complex from E.coli

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