9SRX: Mlc repressor

Cryo-EM structure of the Mlc repressor in complex with the glucose-specific IICB transporter. Determined by electron microscopy at 2.96 Å resolution. Released 22 Jul 2026.

Method: Electron microscopy
Resolution: 2.96 Å
Organism: Escherichia coli
Chains: 12
Atoms: 25,660
Mol. weight: 606.35 kDa
Ligands: ZN, BGC
Released: 22 Jul 2026

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

Secondary structure: helices and β-sheets

9SRX contains 174 α-helices and 114 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: 15 helices, 19 β-strands

Element	Residues	Length	Sheet
α-helix	16-27	12
α-helix	35-39	5
α-helix	47-56	10
β-strand	60	1	33
β-strand	80	1	33
β-strand	86-93	8	34
β-strand	96-103	8	34
β-strand	108-115	8	34
α-helix	124-137	14
β-strand	146-152	7	34
β-strand	156-158	3	35
β-strand	163-166	4	35
β-strand	176	1	35
α-helix	181-186	6
β-strand	190-193	4	34
α-helix	195-205	11
β-strand	215-220	6	36
β-strand	224-230	7	36
β-strand	233-234	2	36
α-helix	245-247	3
β-strand	249	1	37
β-strand	256	1	38
β-strand	262	1	38
β-strand	264	1	37
α-helix	265-267	3
α-helix	271-282	12
α-helix	297-306	10
α-helix	311-333	23
β-strand	337-341	5	36
α-helix	343-347	5
α-helix	348-362	15
β-strand	372-375	4	36
α-helix	386-396	11
α-helix	398-403	6

Chains B and C: 15 helices, 20 β-strands

Element	Residues	Length	Sheet
α-helix	15-27	13
α-helix	35-39	5
α-helix	47-56	10
β-strand	86-93	8	27
β-strand	96-103	8	27
β-strand	108-115	8	27
α-helix	124-138	15
β-strand	146-152	7	27
β-strand	156-158	3	28
β-strand	163-166	4	28
β-strand	167	1	29
β-strand	170	1	29
β-strand	176	1	28
α-helix	181-186	6
β-strand	190-193	4	27
α-helix	195-205	11
β-strand	215-220	6	30
β-strand	224-230	7	30
β-strand	233-234	2	30
β-strand	243	1	30
α-helix	245-247	3
β-strand	249	1	31
β-strand	256	1	32
β-strand	262	1	32
β-strand	264	1	31
α-helix	265-267	3
α-helix	271-282	12
α-helix	297-306	10
α-helix	309-333	25
β-strand	337-341	5	30
α-helix	343-347	5
α-helix	348-362	15
β-strand	372-375	4	30
α-helix	386-396	11
α-helix	398-403	6

Chain D: 15 helices, 19 β-strands

Element	Residues	Length	Sheet
α-helix	16-27	12
α-helix	35-39	5
α-helix	47-56	10
β-strand	60	1	19
β-strand	80	1	19
β-strand	86-93	8	20
β-strand	96-103	8	20
β-strand	108-115	8	20
α-helix	124-137	14
β-strand	146-152	7	20
β-strand	156-158	3	21
β-strand	163-166	4	21
β-strand	176	1	21
α-helix	181-186	6
β-strand	190-193	4	20
α-helix	195-205	11
β-strand	215-220	6	22
β-strand	224-230	7	22
β-strand	233-234	2	22
α-helix	245-247	3
β-strand	249	1	23
β-strand	256	1	24
β-strand	262	1	24
β-strand	264	1	23
α-helix	265-267	3
α-helix	271-282	12
α-helix	297-306	10
α-helix	309-333	25
β-strand	337-341	5	22
α-helix	343-347	5
α-helix	348-362	15
β-strand	372-375	4	22
α-helix	386-396	11
α-helix	398-403	6

Chains E and H: 5 helices, 4 β-strands

Element	Residues	Length	Sheet
α-helix	403-408	6
α-helix	412-414	3
β-strand	417-420	4	26
β-strand	424-428	5	26
α-helix	432-434	3
α-helix	437-442	6
β-strand	448-451	4	26
β-strand	454-458	5	26
α-helix	464-475	12

Chains F and G: 4 helices, 4 β-strands

Element	Residues	Length	Sheet
α-helix	403-408	6
α-helix	412-414	3
β-strand	417-420	4	25
β-strand	424-428	5	25
α-helix	437-442	6
β-strand	448-451	4	25
β-strand	454-458	5	25
α-helix	464-475	12

Chains I, J, K and L: 24 helices, 5 β-strands

Element	Residues	Length	Sheet
α-helix	5-21	17
α-helix	23-34	12
α-helix	42-57	16
α-helix	59-70	12
β-strand	75	1	6
α-helix	76-101	26
α-helix	105-110	6
α-helix	117-135	19
α-helix	142-147	6
α-helix	149-152	4
α-helix	153-184	32
α-helix	185-189	5
α-helix	191-205	15
α-helix	211-220	10
β-strand	225-226	2	7
β-strand	232-233	2	7
α-helix	236-242	7
α-helix	249-252	4
α-helix	253-255	3
α-helix	256-260	5
α-helix	261-271	11
α-helix	277-289	13
α-helix	290-294	5
α-helix	298-305	8
α-helix	310-329	20
β-strand	332	1	8
α-helix	341-346	6
β-strand	352	1	8
α-helix	356-379	24

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
PTS system glucose-specific EIICB component	E, F, G, H, I, J, K, L	protein	477	Escherichia coli	P69786 (AlphaFold model)
DNA-binding transcriptional repressor Mlc	A, B, C, D	protein	455	Escherichia coli	P50456 (AlphaFold model)

Sequence of entity 1 (E, F, G, H, I, J, K, L), FASTA

>9SRX_1 PTS system glucose-specific EIICB component (chains E, F, G, H, I, J, K, L)
MFKNAFANLQKVGKSLMLPVSVLPIAGILLGVGSANFSWLPAVVSHVMAEAGGSVFANMP
LIFAIGVALGFTNNDGVSALAAVVAYGIMVKTMAVVAPLVLHLPAEEIASKHLADTGVLG
GIISGAIAAYMFNRFYRIKLPEYLGFFAGKRFVPIISGLAAIFTGVVLSFIWPPIGSAIQ
TFSQWAAYQNPVVAFGIYGFIERCLVPFGLHHIWNVPFQMQIGEYTNAAGQVFHGDIPRY
MAGDPTAGKLSGGFLFKMYGLPAAAIAIWHSAKPENRAKVGGIMISAALTSFLTGITEPI
EFSFMFVAPILYIIHAILAGLAFPICILLGMRDGTSFSHGLIDFIVLSGNSSKLWLFPIV
GIGYAIVYYTIFRVLIKALDLKTPGREDATEDAKATGTSEMAPALVAAFGGKENITNLDA
CITRLRVSVADVSKVDQAGLKKLGAAGVVVAGSGVQAIFGTKSDNLKTEMDEYIRNH

Sequence of entity 2 (A, B, C, D), FASTA

>9SRX_2 DNA-binding transcriptional repressor Mlc (chains A, B, C, D)
MGGSHHHHHHGMASMTGGQQMGRDLYDDDDKDRWGSELEVLFQGPKLMVAENQPGHIDQI
KQTNAGAVYRLIDQLGPVSRIDLSRLAQLAPASITKIVREMLEAHLVQELEIKEAGNRGR
PAVGLVVETEAWHYLSLRISRGEIFLALRDLSSKLVVEESQELALKDDLPLLDRIISHID
QFFIRHQKKLERLTSIAITLPGIIDTENGIVHRMPFYEDVKEMPLGEALEQHTGVPVYIQ
HDISAWTMAEALFGASRGARDVIQVVIDHNVGAGVITDGHLLHAGSSSLVEIGHTQVDPY
GKRCYCGNHGCLETIASVDSILELAQLRLNQSMSSMLHGQPLTVDSLCQAALRGDLLAKD
IITGVGAHVGRILAIMVNLFNPQKILIGSPLSKAADILFPVISDSIRQQALPAYSQHISV
ESTQFSNQGTMAGAALVKDAMYNGSLLIRLLQGLE

Ligands and cofactors

ID	Name	Formula	Copies
ZN	Zinc ion	Zn	4
BGC	beta-D-glucopyranose	C6 H12 O6	4

Primary citation

Structural basis of Mlc-mediated transcriptional regulation of carbohydrate metabolism. Roth, P., Fender, I., Jeckelmann, J.M. et al. Nat Commun (2026) 17. DOI 10.1038/s41467-026-75270-8 · PubMed

Other PDB entries of the same protein (UniProt P69786 (AlphaFold model), which also has an AlphaFold model), best resolution first:

3BP3 1.65 Å, Crystal structure of EIIB
9HNP 2.53 Å, Cryo-EM structure of the glucose-specific PTS transporter IICB from E. coli in an…
8QSR 2.56 Å, Cryo-EM structure of the glucose-specific PTS transporter IICB from E. coli in the…
3BP8 2.85 Å, Crystal structure of Mlc/EIIB complex
8QST 2.89 Å, Cryo-EM structure of the glucose-specific PTS transporter IICB from E. coli in the…
1IBA Glucose permease (domain iib), NMR, 11 structures
1O2F Complex of enzyme iiaglc and iibglc phosphocarrier protein hpr from escherichia coli…
9A3B Model of E. coli PtsG by in-cell photo-crosslinking MS and deep learning

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