Escherichia coli K-12 substr. MG1655 Enzyme: β-galactosidase

Gene: lacZ Accession Numbers: EG10527 (EcoCyc), b0344, ECK0341

Synonyms: β-D-galactoside galactohydrolase, β-D-galactosidase, lactase

Regulation Summary Diagram: ?

Regulation summary diagram for lacZ

Subunit composition of β-galactosidase = [LacZ]4
         β-galactosidase monomer = LacZ

β-galactosidase is a bifunctional enzyme that hydrolyses lactose to galactose plus glucose and converts lactose to allolactose. The enzyme requires Mg2+ or Mn2+ for full activity [Tenu72, Sinnott78, Sutendra07] plus a monovalent cation, usually Na+ or K+ [Juers01, Xu04].

Purification of β-galactosidase was achieved during the middle of the 20th century from E. coli strain ML 308 [Wallenfels57, Hu59, Cohn51] and from strain K-12 [Lederberg50, Craven65]. It was subsequently used as a model system to analyse how the response to a change in environment was regulated at the cellular level, specifically addressing questions of enzyme 'adaption' or enzyme 'induction' as it was then called (reviewed by [Cohn57]. These studies resulted in the elucidation of a pathway of negative control of β-galactosidase synthesis and led to the description of the operon model for gene regulation [Jacob61].

lacZ forms an operon with lacY (encoding lactose permease) and lacA (a transacetylase). Expression of the lac operon is repressed by LacI which binds to the lac operator [Bourgeois65, Gilbert66]. In the presence of allolactose - the physiological inducer [Jobe72] - LacI binding to the operator is reduced leading to expression of the lac operon and production of the proteins necessary for lactose utilisation (reviewed by [Lewis05]).

β-galactosidase is a large tetrameric molecule made up of 4 identical subunits. The tetramer has 4 active sites but it takes two monomers to complete an active site. Each monomer contains 5 domains including domain 3 which has an α/β barrel structure that interacts with the loop structure from domain 2 of a separate monomer to form much of the active site [Craven65, Steers65, Jacobson94] (reviewed by [Matthews05]).

Deletion of residues from the amino terminus results in inactive dimers. Supplying peptides that include the missing residues restores the tetrameric structure and catalytic activity. This process is known as α-complementation and is the basis for the blue/white screening technique used in vector based gene cloning [Ullmann65, Ullmann67, Langley75] (reviewed by [Ullmann92]).

Genetic fusions between the lac repressor and lacZ produce fully active repressor linked to active β-galactosidase. The fusions generate hybrid proteins whose amino terminus corresponds to a portion of the lac repressor and whose carboxy terminus corresponds to β-galactosidase [MullerHill74]. The technique of generating fusions to produce hybrid proteins has been extended to allow the fusion of lacZ to virtually any gene of interest and has been widely used for gene and protein detection and in studies of gene regulation and protein localisation (reviewed in [Silhavy85].

Additional reviews: [Cohn89, Beckwith67, Wallenfels72]

Citations: [Shuman03, Herring03, Hogness55, Rotman54, Cohn52, Cohn53, Juers03, Juers00, Sinnott78a, Gallagher98, Gallagher97, Gallagher99, Bartesaghi14, Wheatley15]

Gene Citations: [Miller78, Murakawa91, McCormick91]

Locations: cytosol

Map Position: [362,455 <- 365,529] (7.81 centisomes, 28°)
Length: 3075 bp / 1024 aa

Molecular Weight of Polypeptide: 116.48 kD (from nucleotide sequence)

Molecular Weight of Multimer: 540.0 kD (experimental) [Craven65]

pI: 5.55

Unification Links: ASAP:ABE-0001183 , CGSC:576 , DIP:DIP-10081N , EchoBASE:EB0522 , EcoGene:EG10527 , EcoliWiki:b0344 , ModBase:P00722 , OU-Microarray:b0344 , PortEco:lacZ , Pride:P00722 , Protein Model Portal:P00722 , RefSeq:NP_414878 , RegulonDB:EG10527 , SMR:P00722 , String:511145.b0344 , UniProt:P00722

Relationship Links: CAZy:IN-FAMILY:GH2 , InterPro:IN-FAMILY:IPR004199 , InterPro:IN-FAMILY:IPR006101 , InterPro:IN-FAMILY:IPR006102 , InterPro:IN-FAMILY:IPR006103 , InterPro:IN-FAMILY:IPR006104 , InterPro:IN-FAMILY:IPR008979 , InterPro:IN-FAMILY:IPR011013 , InterPro:IN-FAMILY:IPR013781 , InterPro:IN-FAMILY:IPR013812 , InterPro:IN-FAMILY:IPR014718 , InterPro:IN-FAMILY:IPR017853 , InterPro:IN-FAMILY:IPR023230 , InterPro:IN-FAMILY:IPR023232 , InterPro:IN-FAMILY:IPR023933 , PDB:Structure:1BGL , PDB:Structure:1BGM , PDB:Structure:1DP0 , PDB:Structure:1F49 , PDB:Structure:1F4A , PDB:Structure:1F4H , PDB:Structure:1GHO , PDB:Structure:1HN1 , PDB:Structure:1JYN , PDB:Structure:1JYV , PDB:Structure:1JYW , PDB:Structure:1JYX , PDB:Structure:1JYY , PDB:Structure:1JYZ , PDB:Structure:1JZ0 , PDB:Structure:1JZ1 , PDB:Structure:1JZ2 , PDB:Structure:1JZ3 , PDB:Structure:1JZ4 , PDB:Structure:1JZ5 , PDB:Structure:1JZ6 , PDB:Structure:1JZ7 , PDB:Structure:1JZ8 , PDB:Structure:1PX3 , PDB:Structure:1PX4 , PDB:Structure:3CZJ , PDB:Structure:3DYM , PDB:Structure:3DYO , PDB:Structure:3DYP , PDB:Structure:3E1F , PDB:Structure:3I3B , PDB:Structure:3I3D , PDB:Structure:3I3E , PDB:Structure:3IAP , PDB:Structure:3IAQ , PDB:Structure:3J7H , PDB:Structure:3MUY , PDB:Structure:3MUZ , PDB:Structure:3MV0 , PDB:Structure:3MV1 , PDB:Structure:3SEP , PDB:Structure:3T08 , PDB:Structure:3T09 , PDB:Structure:3T0A , PDB:Structure:3T0B , PDB:Structure:3T0D , PDB:Structure:3T2O , PDB:Structure:3T2P , PDB:Structure:3T2Q , PDB:Structure:3VD3 , PDB:Structure:3VD4 , PDB:Structure:3VD5 , PDB:Structure:3VD7 , PDB:Structure:3VD9 , PDB:Structure:3VDA , PDB:Structure:3VDB , PDB:Structure:3VDC , PDB:Structure:4CKD , PDB:Structure:4DUV , PDB:Structure:4DUW , PDB:Structure:4DUX , PDB:Structure:4TTG , Pfam:IN-FAMILY:PF00703 , Pfam:IN-FAMILY:PF02836 , Pfam:IN-FAMILY:PF02837 , Pfam:IN-FAMILY:PF02929 , Prints:IN-FAMILY:PR00132 , Prosite:IN-FAMILY:PS00608 , Prosite:IN-FAMILY:PS00719 , Smart:IN-FAMILY:SM01038

In Paralogous Gene Group: 108 (3 members)

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Genetic Regulation Schematic: ?

Genetic regulation schematic for lacZ

GO Terms:

Biological Process: GO:0005990 - lactose catabolic process Inferred from experiment [Craig12, Cook62]
GO:0005975 - carbohydrate metabolic process Inferred by computational analysis [GOA01a]
GO:0008152 - metabolic process Inferred by computational analysis [UniProtGOA11a]
Molecular Function: GO:0000287 - magnesium ion binding Inferred from experiment Inferred by computational analysis [GOA06, Tenu72, Juers00]
GO:0004565 - beta-galactosidase activity Inferred from experiment Inferred by computational analysis [GOA01, GOA01a, Craven65]
GO:0031420 - alkali metal ion binding Inferred from experiment [Neville67, Juers01]
GO:0003824 - catalytic activity Inferred by computational analysis [GOA01a]
GO:0004553 - hydrolase activity, hydrolyzing O-glycosyl compounds Inferred by computational analysis [GOA01a]
GO:0016787 - hydrolase activity Inferred by computational analysis [UniProtGOA11a]
GO:0016798 - hydrolase activity, acting on glycosyl bonds Inferred by computational analysis [UniProtGOA11a, GOA06, GOA01a]
GO:0030246 - carbohydrate binding Inferred by computational analysis [GOA01a]
GO:0046872 - metal ion binding Inferred by computational analysis [UniProtGOA11a]
Cellular Component: GO:0009341 - beta-galactosidase complex Inferred from experiment Inferred by computational analysis [GOA01a, Craven65, Jacobson94]
GO:0005829 - cytosol Inferred by curator
GO:0043231 - intracellular membrane-bounded organelle Inferred by computational analysis [Gaudet10]

MultiFun Terms: metabolism carbon utilization carbon compounds

Essentiality data for lacZ knockouts: ?

Growth Medium Growth? T (°C) O2 pH Osm/L Growth Observations
LB enriched Yes 37 Aerobic 6.95   Yes [Gerdes03, Comment 1]

Last-Curated ? 20-Apr-2015 by Mackie A , Macquarie University

Enzymatic reaction of: lactose galactohydrolase (β-galactosidase)

EC Number:

α-lactose + H2O <=> β-D-galactose + β-D-glucopyranose

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

Alternative Substrates for α-lactose: o-nitrophenyl-β-galactoside [Cohn51 , Lederberg50 ]

In Pathways: lactose degradation III

Cofactors or Prosthetic Groups: Mg2+ [Hu59]

Inhibitors (Competitive): conduritol C cis-epoxide , β-D-galactopyranosyl trimethylammonium bromide [Case73] , o-nitrophenol β-thiogalactoside [Sinnott71] , phenyl-1-thio-β-D-galactopyranoside [Sinnott71] , D-galactal , 2-aminogalactopyranose [Huber82, Helmward89] , β-D-galactose [Huber82, Helmward89]

Inhibitors (Unknown Mechanism): a chelator [Wallenfels72] , 2-deoxy-2-fluoro-β-D-galactopyranosyl fluoride [Withers88, Helmward89] , 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide [Helmward89] , (1/2,5,6)-2-(3-azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol [Helmward89] , isopropyl β-D-galactopyranoside [Helmward89] , a heavy metal ion [Wallenfels72] , an alkylmercury [Wallenfels72] , cysteamine [Wallenfels72] , D-galactosylamine [Helmward89] , 1,5-dideoxy-1,5-imino-D-galactitol [Helmward89] , 5-amino-5-deoxy-D-galactopyranoside [Helmward89] , 2-mercaptoethanol [Wallenfels72] , n-propanol [Wallenfels72] , ethanolamine [Wallenfels72] , ethylenediamine [Wallenfels72]

pH(opt): 7 [Cohn51]

Enzymatic reaction of: β-galactosidase

EC Number: 5.4.1.-

α-lactose <=> allolactose

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

Reversibility of this reaction is unspecified.

Sequence Features

Protein sequence of beta-galactosidase monomer with features indicated

Feature Class Location Common Name Citations Comment
Cleavage-of-Initial-Methionine 1  
[Fowler78, Brown66]
Chain 2 -> 1024  
UniProt: Beta-galactosidase;
Amino-Acid-Sites-That-Bind 103  
UniProt: Substrate.
Metal-Binding-Site 202  
UniProt: Sodium.
Mutagenesis-Variant 202  
[Xu04, UniProt11]
[Xu04, UniProt11]
D → E or N: Causes a significant decrease in binding affinity in the absence of monovalent cations or in the presence of potassium ions, but only a moderate decrease in the presence of sodium ions.
D → F: Obliterates all binding and catalysis.
Amino-Acid-Site 358  
UniProt: Transition state stabilizer; Sequence Annotation Type: site.
Mutagenesis-Variant 358  
[UniProt11, Roth98, UniProt11]
H → D, F, L or N: Less stable to heat than wild-type. Causes significant destabilizations of the first transition state.
Amino-Acid-Site 392  
UniProt: Transition state stabilizer; Sequence Annotation Type: site.
Mutagenesis-Variant 392  
[Huber01, UniProt11]
H → E, F or K: Essentially inactive unless very rapid purification. Causes very large destabilizations of the transition state.
Metal-Binding-Site 417  
[Juers00, UniProt15]
UniProt: Magnesium 1.
Metal-Binding-Site 419  
[Juers00, UniProt15]
UniProt: Magnesium 1.
Metal-Binding-Site 462  
[Juers00, UniProt15]
UniProt: Magnesium 1.
Active-Site 462  
[Herrchen84, UniProt15]
UniProt: Proton donor.
Mutagenesis-Variant 462  
[MartinezBilbao95, UniProt11]
UniProt: Slowly inactivates galactosidase activity by reducing the binding of magnesium. It increases binding specificity.
Mutagenesis-Variant 538  
[Juers01, UniProt11]
UniProt: 10000-fold decrease in the beta- galactosidase activity.
Protein-Segment 538 -> 541  
UniProt: Substrate binding; Sequence Annotation Type: region of interest;
Active-Site 538 active site nucleophile
[Fowler83, Gebler92]
Mutagenesis-Variant 541  
[Roth96, UniProt11]
H → E, F or N: Poorly reactive with galactosyl substrates. Less stable to heat than wild-type.
Metal-Binding-Site 598  
[Juers00, UniProt15]
UniProt: Magnesium 2.
Metal-Binding-Site 602  
UniProt: Sodium; via carbonyl oxygen.
Mutagenesis-Variant 602  
[Juers01, UniProt11]
UniProt: Decreases the stability of the loop 794-804.
Metal-Binding-Site 605  
UniProt: Sodium.
Mutagenesis-Variant 795  
[Juers03, UniProt11]
UniProt: It forces the apoenzyme to adopt the closed rather than the open conformation. Reduces the binding affinity.
Mutagenesis-Variant 798  
[Sutendra07, UniProt11]
[Sutendra07, UniProt11]
E → D or Q: Small increase of the catalytic efficiency, when the sodium concentration increases.
E → A or L: The catalytic efficiency is not increased, when the sodium concentration increases.
Amino-Acid-Sites-That-Bind 1000  
UniProt: Substrate.
Mutagenesis-Variant 1000  
[Huber03, UniProt11]
W → F, G, L or T: Decreases affinity for substrate.

Gene Local Context (not to scale): ?

Gene local context diagram

Transcription Units:

Transcription-unit diagram

Transcription-unit diagram

Transcription-unit diagram

Transcription-unit diagram

Transcription-unit diagram


10/20/97 Gene b0344 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10527; confirmed by SwissProt match.


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Beckwith67: Beckwith JR (1967). "Regulation of the lac operon. Recent studies on the regulation of lactose metabolism in Escherichia coli support the operon model." Science 156(3775);597-604. PMID: 5337175

Bourgeois65: Bourgeois S, Cohn M, Orgel LE (1965). "Suppression of and complementation among mutants of the regulatory gene of the lactose operon of Escherichia coli." J Mol Biol 14(1);300-2. PMID: 5327656

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Case73: Case GS, Sinnott ML, Tenu JP (1973). "The role of magnesium ions in beta-galactosidase hydrolyses. Studies on charge and shape of the beta-galactopyranosyl binding site." Biochem J 1973;133(1);99-104. PMID: 4721625

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Cohn52: Cohn M, Torriani AM (1952). "Immunochemical studies with the beta-galactosidase and structurally related proteins of Escherichia coli." J Immunol 69(5);471-91. PMID: 13011306

Cohn53: Cohn M, Torriani AM (1953). "The relationships in biosynthesis of the beta-galactosidase- and Pz-proteins in Escherichia coli." Biochim Biophys Acta 10(2);280-9. PMID: 13051404

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Cohn89: Cohn M (1989). "The way it was: a commentary on 'Studies on the Induced Synthesis of beta-galactosidase in Escherichia coli: the Kinetics and Mechanism of Sulfur Incorporation'." Biochim Biophys Acta 1000;109-12. PMID: 2505844

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Craig12: Craig DB, Schwab T, Sterner R (2012). "Random mutagenesis suggests that sequence errors are not a major cause of variation in the activity of individual molecules of β-galactosidase." Biochem Cell Biol 90(4);540-7. PMID: 22475386

Craven65: Craven GR, Steers E, Anfinsen CB (1965). "Purification, Composition, and Molecular Weight of the β-Galactosidase of Escherichia coli K12." J Biol Chem 240;2468-77. PMID: 14304855

Fowler78: Fowler AV, Zabin I (1978). "Amino acid sequence of beta-galactosidase. XI. Peptide ordering procedures and the complete sequence." J Biol Chem 253(15);5521-5. PMID: 97298

Fowler83: Fowler AV, Smith PJ (1983). "The active site regions of lacZ and ebg beta-galactosidases are homologous." J Biol Chem 258(17);10204-7. PMID: 6411710

Gallagher97: Gallagher CN, Huber RE (1997). "Monomer-dimer equilibrium of uncomplemented M15 beta-galactosidase from Escherichia coli." Biochemistry 36(6);1281-6. PMID: 9063875

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Gallagher99: Gallagher CN, Huber RE (1999). "Stabilities of uncomplemented and complemented M15 beta-galactosidase (Escherichia coli) and the relationship to alpha-complementation." Biochem Cell Biol 77(2);109-18. PMID: 10438145

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Gebler92: Gebler JC, Aebersold R, Withers SG (1992). "Glu-537, not Glu-461, is the nucleophile in the active site of (lac Z) beta-galactosidase from Escherichia coli." J Biol Chem 267(16);11126-30. PMID: 1350782

Gerdes03: Gerdes SY, Scholle MD, Campbell JW, Balazsi G, Ravasz E, Daugherty MD, Somera AL, Kyrpides NC, Anderson I, Gelfand MS, Bhattacharya A, Kapatral V, D'Souza M, Baev MV, Grechkin Y, Mseeh F, Fonstein MY, Overbeek R, Barabasi AL, Oltvai ZN, Osterman AL (2003). "Experimental determination and system level analysis of essential genes in Escherichia coli MG1655." J Bacteriol 185(19);5673-84. PMID: 13129938

Gilbert66: Gilbert W, Muller-Hill B (1966). "Isolation of the lac repressor." Proc Natl Acad Sci U S A 56(6);1891-8. PMID: 16591435

GOA01: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA01a: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

GOA06: GOA, SIB (2006). "Electronic Gene Ontology annotations created by transferring manual GO annotations between orthologous microbial proteins."

Helmward89: Helmward Z "Handbook of Enzyme Inhibitors. 2nd, revised and enlarged edition." Weinheim, Federal Republic of Germany ; New York, NY, USA , 1989.

Herrchen84: Herrchen M, Legler G (1984). "Identification of an essential carboxylate group at the active site of lacZ beta-galactosidase from Escherichia coli." Eur J Biochem 1984;138(3);527-31. PMID: 6420154

Herring03: Herring CD, Glasner JD, Blattner FR (2003). "Gene replacement without selection: regulated suppression of amber mutations in Escherichia coli." Gene 311;153-63. PMID: 12853150

Hogness55: Hogness DS, Cohn M, Monod J (1955). "Studies on the induced synthesis of beta-galactosidase in Escherichia coli: the kinetics and mechanism of sulfur incorporation." Biochim Biophys Acta 16(1);99-116. PMID: 14363236

Hu59: Hu AS, Wolfe RG, Reithel FJ (1959). "The preparation and purification of beta-galactosidase from Escherichia coli, ML 308." Arch Biochem Biophys 81(2);500-7. PMID: 13638015

Huber01: Huber RE, Hlede IY, Roth NJ, McKenzie KC, Ghumman KK (2001). "His-391 of beta-galactosidase (Escherichia coli) promotes catalyses by strong interactions with the transition state." Biochem Cell Biol 79(2);183-93. PMID: 11310566

Huber03: Huber RE, Hakda S, Cheng C, Cupples CG, Edwards RA (2003). "Trp-999 of beta-galactosidase (Escherichia coli) is a key residue for binding, catalysis, and synthesis of allolactose, the natural lac operon inducer." Biochemistry 42(6);1796-803. PMID: 12578395

Huber82: Huber RE, Gaunt MT (1982). "The inhibition of beta-galactosidase (Escherichia coli) by amino sugars and amino alcohols." Can J Biochem 1982;60(6);608-12. PMID: 6811114

Jacob61: Jacob F, Monod J (1961). "Genetic regulatory mechanisms in the synthesis of proteins." J Mol Biol 3;318-56. PMID: 13718526

Jacobson94: Jacobson RH, Zhang XJ, DuBose RF, Matthews BW (1994). "Three-dimensional structure of beta-galactosidase from E. coli." Nature 1994;369(6483);761-6. PMID: 8008071

Jobe72: Jobe A, Bourgeois S (1972). "lac Repressor-operator interaction. VI. The natural inducer of the lac operon." J Mol Biol 69(3);397-408. PMID: 4562709

Juers00: Juers DH, Jacobson RH, Wigley D, Zhang XJ, Huber RE, Tronrud DE, Matthews BW (2000). "High resolution refinement of beta-galactosidase in a new crystal form reveals multiple metal-binding sites and provides a structural basis for alpha-complementation." Protein Sci 9(9);1685-99. PMID: 11045615

Juers01: Juers DH, Heightman TD, Vasella A, McCarter JD, Mackenzie L, Withers SG, Matthews BW (2001). "A structural view of the action of Escherichia coli (lacZ) beta-galactosidase." Biochemistry 40(49);14781-94. PMID: 11732897

Juers03: Juers DH, Hakda S, Matthews BW, Huber RE (2003). "Structural basis for the altered activity of Gly794 variants of Escherichia coli beta-galactosidase." Biochemistry 42(46);13505-11. PMID: 14621996

Langley75: Langley KE, Villarejo MR, Fowler AV, Zamenhof PJ, Zabin I (1975). "Molecular basis of beta-galactosidase alpha-complementation." Proc Natl Acad Sci U S A 72(4);1254-7. PMID: 1093175

Lederberg50: Lederberg J (1950). "The beta-d-galactosidase of Escherichia coli, strain K-12." J Bacteriol 60(4);381-92. PMID: 14784466

Lewis05: Lewis M (2005). "The lac repressor." C R Biol 328(6);521-48. PMID: 15950160

MartinezBilbao95: Martinez-Bilbao M, Gaunt MT, Huber RE (1995). "E461H-beta-galactosidase (Escherichia coli): altered divalent metal specificity and slow but reversible metal inactivation." Biochemistry 34(41);13437-42. PMID: 7577931

Matthews05: Matthews BW (2005). "The structure of E. coli beta-galactosidase." C R Biol 328(6);549-56. PMID: 15950161

McCormick91: McCormick JR, Zengel JM, Lindahl L (1991). "Intermediates in the degradation of mRNA from the lactose operon of Escherichia coli." Nucleic Acids Res 1991;19(10);2767-76. PMID: 1710346

Miller78: Miller JH, Reznikoff WS (eds) "The Operon." Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1978.

MullerHill74: Muller-Hill B, Kania J (1974). "Lac repressor can be fused to beta-galactosidase." Nature 249(457);561-3. PMID: 4599764

Murakawa91: Murakawa GJ, Kwan C, Yamashita J, Nierlich DP (1991). "Transcription and decay of the lac messenger: role of an intergenic terminator." J Bacteriol 1991;173(1);28-36. PMID: 1702782

Neville67: Neville MC, Ling GN (1967). "Synergistic activation of beta-galactosidase by Na and Cs." Arch Biochem Biophys 118(3);596-610. PMID: 4860414

Roth96: Roth NJ, Huber RE (1996). "The beta-galactosidase (Escherichia coli) reaction is partly facilitated by interactions of His-540 with the C6 hydroxyl of galactose." J Biol Chem 271(24);14296-301. PMID: 8662937

Roth98: Roth NJ, Rob B, Huber RE (1998). "His-357 of beta-galactosidase (Escherichia coli) interacts with the C3 hydroxyl in the transition state and helps to mediate catalysis." Biochemistry 37(28);10099-107. PMID: 9665715

Rotman54: Rotman B, Spiegelman S (1954). "On the origin of the carbon in the induced synthesis beta-galactosidase in Escherichia coli." J Bacteriol 68(4);419-29. PMID: 13201546

Shuman03: Shuman HA, Silhavy TJ (2003). "The art and design of genetic screens: Escherichia coli." Nat Rev Genet 4(6);419-31. PMID: 12776212

Silhavy85: Silhavy TJ, Beckwith JR (1985). "Uses of lac fusions for the study of biological problems." Microbiol Rev 49(4);398-418. PMID: 3005818

Sinnott71: Sinnott ML (1971). "β-galactosidase-catalysed hydrolysis of β-D-galactopyranosyl azide." Biochem J 1971;125(3);717-9. PMID: 4947657

Sinnott78: Sinnott ML, Withers SG (1978). "The necessity of magnesium cation for acid assistance aglycone departure in catalysis by Escherichia coli (lacZ) beta-galactosidase." Biochem J 175(2);539-46. PMID: 105722

Sinnott78a: Sinnott ML (1978). "Ions, ion-pairs and catalysis by the lacZ beta-galactosidase of Escherichia coli." FEBS Lett 1978;94(1);1-9. PMID: 100348

Steers65: Steers E, Craven GR, Anfinsen CB, Bethune JL (1965). "Evidence for nonidentical chains in the beta-galactosidase of Escherichia coli K12." J Biol Chem 240;2478-84. PMID: 14304856

Steers67: Steers E, Shifrin S (1967). "Characterization of the beta-galactosidase from a lactose-negative, complementing mutant of Escherichia coli K12." Biochim Biophys Acta 133(3);454-62. PMID: 4962166

Sutendra07: Sutendra G, Wong S, Fraser ME, Huber RE (2007). "Beta-galactosidase (Escherichia coli) has a second catalytically important Mg2+ site." Biochem Biophys Res Commun 352(2);566-70. PMID: 17126292

Tenu72: Tenu JP, Viratelle OM, Yon J (1972). "Kinetic study of the activation process of -galactosidase from Escherichia coli by Mg 2+." Eur J Biochem 1972;26(1);112-8. PMID: 4625429

Ullmann65: Ullmann A, Perrin D, Jacob F, Monod J (1965). "[Identification, by in vitro complementation and purification, of a peptide fraction of Escherichia coli beta-galactosidase]." J Mol Biol 12(3);918-23. PMID: 4285628

Ullmann67: Ullmann A, Jacob F, Monod J (1967). "Characterization by in vitro complementation of a peptide corresponding to an operator-proximal segment of the beta-galactosidase structural gene of Escherichia coli." J Mol Biol 24(2);339-43. PMID: 5339877

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UniProt09: UniProt Consortium (2009). "UniProt version 15.8 released on 2009-10-01 00:00:00." Database.

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Other References Related to Gene Regulation

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Miroslavova06: Miroslavova NS, Mitchell JE, Tebbutt J, Busby SJ (2006). "Recruitment of RNA polymerase to Class II CRP-dependent promoters is improved by a second upstream-bound CRP molecule." Biochem Soc Trans 34(Pt 6);1075-8. PMID: 17073754

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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