1LBI: Lac repressor

Lac repressor. Determined by X-ray diffraction at 2.7 Å resolution. Released 11 Jul 1996.

Method: X-ray diffraction
Resolution: 2.7 Å
Organism: Escherichia coli
Chains: 4
Atoms: 8,872
Mol. weight: 154.63 kDa
Released: 11 Jul 1996

Explore 1LBI in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

1LBI contains 47 α-helices and 62 β-strands across 4 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: 13 helices, 16 β-strands

Element	Residues	Length	Sheet
β-strand	63-69	7	1
α-helix	74-90	17
β-strand	93-99	7	1
α-helix	100	1
α-helix	103-115	13
β-strand	121-125	5	1
α-helix	131-138	8
β-strand	145-147	3	1
β-strand	159-161	3	2
α-helix	165-177	13
β-strand	182-186	5	3
α-helix	193-207	15
β-strand	214-217	4	3
α-helix	222-233	12
β-strand	241-244	4	3
α-helix	247-258	12
α-helix	262-263	2
β-strand	264	1	4
β-strand	268	1	4
β-strand	269-271	3	3
β-strand	274	1	5
α-helix	279-281	3
α-helix	285-286	2
β-strand	287	1	3
β-strand	288-290	3	5
α-helix	293-308	16
β-strand	317-319	3	2
β-strand	322-324	3	5
α-helix	339-356	18

Chain B: 11 helices, 17 β-strands

Element	Residues	Length	Sheet
β-strand	63-68	6	1
α-helix	74-89	16
β-strand	93-98	6	1
α-helix	105-116	12
β-strand	121-124	4	1
α-helix	130-137	8
β-strand	145-147	3	1
β-strand	158	1	1
β-strand	160-161	2	6
α-helix	163-176	14
β-strand	182-186	5	7
α-helix	192-205	14
β-strand	215-217	3	7
α-helix	222-234	13
β-strand	241-244	4	7
α-helix	248-258	11
β-strand	264	1	8
β-strand	268	1	8
β-strand	269-271	3	7
β-strand	274	1	9
α-helix	277-281	5
α-helix	285-286	2
β-strand	287	1	7
β-strand	288-290	3	9
α-helix	293-308	16
β-strand	318-319	2	6
β-strand	322-324	3	9
α-helix	339-356	18

Chain C: 12 helices, 14 β-strands

Element	Residues	Length	Sheet
β-strand	64-69	6	10
α-helix	74-89	16
β-strand	94-99	6	10
α-helix	100	1
α-helix	104-116	13
β-strand	121-124	4	10
α-helix	130-138	9
β-strand	145-147	3	10
β-strand	158-161	4	10
α-helix	163-176	14
β-strand	182-186	5	11
α-helix	192-207	16
β-strand	214-217	4	11
α-helix	222-233	12
β-strand	241-244	4	11
α-helix	247-259	13
β-strand	264	1	12
β-strand	268	1	12
β-strand	269-274	6	11
α-helix	279-281	3
α-helix	285-286	2
β-strand	287-290	4	11
α-helix	293-309	17
β-strand	316-319	4	10
β-strand	322-324	3	11
α-helix	339-353	15

Chain D: 11 helices, 15 β-strands

Element	Residues	Length	Sheet
β-strand	64-69	6	10
α-helix	74-90	17
β-strand	94-99	6	10
α-helix	105-116	12
β-strand	121-125	5	10
α-helix	131-139	9
β-strand	145-147	3	10
β-strand	157-161	5	10
α-helix	162	1
α-helix	163-176	14
β-strand	182-186	5	13
α-helix	192-205	14
β-strand	215-217	3	13
α-helix	222-234	13
β-strand	241-244	4	13
α-helix	247-258	12
β-strand	264	1	14
β-strand	268	1	14
β-strand	269-271	3	13
β-strand	272	1	15
α-helix	277-281	5
β-strand	288-290	3	15
α-helix	293-308	16
β-strand	316-319	4	10
β-strand	322-324	3	15
α-helix	341-355	15

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Lac repressor	A, B, C, D	protein	360	Escherichia coli	P03023 (AlphaFold model)

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

>1LBI_1 LAC REPRESSOR (chains A, B, C, D)
MKPVTLYDVAEYAGVSYQTVSRVVNQASHVSAKTREKVEAAMAELNYIPNRVAQQLAGKQ
SLLIGVATSSLALHAPSQIVAAIKSRADQLGASVVVSMVERSGVEACKTAVHNLLAQRVS
GLIINYPLDDQDAIAVEAACTNVPALFLDVSDQTPINSIIFSHEDGTRLGVEHLVALGHQ
QIALLAGPLSSVSARLRLAGWHKYLTRNQIQPIAEREGDWSAMSGFQQTMQMLNEGIVPT
AMLVANDQMALGAMRAITESGLRVGADISVVGYDDTEDSSCYIPPLTTIKQDFRLLGQTS
VDRLLQLSQGQAVKGNQLLPVSLVKRKTTLAPNTQTASPRALADSLMQLARQVSRLESGQ

Primary citation

Crystal structure of the lactose operon repressor and its complexes with DNA and inducer. Lewis, M., Chang, G., Horton, N.C. et al. Science (1996) 271:1247-1254. PubMed

Other PDB entries of the same protein (UniProt P03023 (AlphaFold model), which also has an AlphaFold model), best resolution first:

8GOH 1.1 Å, Homotetramic Antiparallel Coiled-Coil of 23-residues LacI C-terminal tetramerization helix
1JYE 1.7 Å, Structure of a Dimeric Lac Repressor with C-terminal Deletion and K84L Substitution
2P9H 2.0 Å, High resolution structure of the Lactose Repressor bound to IPTG
3EDC 2.1 Å, Crystal Structure of a 1.6-hexanediol Bound Tetrameric Form of Escherichia coli…
1EFA 2.6 Å, Crystal structure of the lac repressor dimer bound to operator and the anti-inducer onpf
1TLF 2.6 Å, Unprecedented quaternary structure of E. Coli lac repressor core tetramer: implications…
4RZS 2.71 Å, Lac repressor engineered to bind sucralose, unliganded tetramer
1JYF 3.0 Å, Structure of the Dimeric Lac Repressor with an 11-residue C-terminal Deletion.
4RZT 3.1 Å, Lac repressor engineered to bind sucralose, sucralose-bound tetramer
1LBH 3.2 Å, Intact lactose operon repressor with gratuitous inducer iptg
2PAF 3.5 Å, Crystal Structure of the Lactose Repressor bound to anti-inducer ONPF in induced state
2PE5 3.5 Å, Crystal Structure of the Lac Repressor bound to ONPG in repressed state

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