|Gene:||tap||Accession Numbers: EG10987 (EcoCyc), b1885, ECK1886|
Synonyms: Tap dimer, MCP-IV, dipeptide chemoreceptor protein, chemotaxis signaling protein IV
Component of: chemotaxis signaling complex - dipeptide sensing (extended summary available)
Subunit composition of methyl accepting chemotaxis protein - dipeptide sensing = [Tap]2
The tap gene product is one of four methyl-accepting chemotaxis proteins (MCPs) in E. coli K-12. MCP-IV interacts with the the periplasmic dipeptide-binding protein DppA to mediate taxis toward dipeptides. Dipeptides are good attractants, tripeptides are poor attractants. Peptides containing D-amino acids are poor attractants [Manson86, Abouhamad91].
E. coli Tap is predicted to be a homodimeric inner membrane protein; the Tap monomer consists of a periplasmic, ligand-sensing domain, two trans-membrane segments (TM1 and TM2) and a cytoplasmic signaling domain containing putative methylation sites [Krikos83, Le96]. Methylation and demethylation of MCPs in E. coli K-12 is catalysed by the CheR methyltransferase and the CheB methylesterase.
The cytoplasmic domains of the four E. coli MCPs have a high degree of sequence similarity [Krikos83, Le96, Alexander07]. Tap contains a HAMP domain (present in histidine kinases, adenylate cyclases, methyl accepting chemotaxis proteins, phosphatases) which is located between the transmembrane region of the molecule and the cytoplasmic signalling region. HAMP domains are thought to mediate input/ouptut signaling (reviewed in [Parkinson10]. E. coli Tap is predicted to form a ternary complexe with the histidine autokinase CheA and the coupling protein CheW.
tap: taxis associated protein
Locations: inner membrane
|Map Position: [1,967,407 <- 1,969,008] (42.4 centisomes, 153°)||Length: 1602 bp / 533 aa|
Molecular Weight of Polypeptide: 57.512 kD (from nucleotide sequence), 65.0 kD (experimental) [Slocum83 ]
Unification Links: ASAP:ABE-0006288 , CGSC:123 , DIP:DIP-10955N , EchoBASE:EB0980 , EcoGene:EG10987 , EcoliWiki:b1885 , Mint:MINT-1309514 , ModBase:P07018 , OU-Microarray:b1885 , PortEco:tap , PR:PRO_000024025 , Protein Model Portal:P07018 , RefSeq:NP_416399 , RegulonDB:EG10987 , SMR:P07018 , String:511145.b1885 , Swiss-Model:P07018 , UniProt:P07018
Relationship Links: InterPro:IN-FAMILY:IPR003122 , InterPro:IN-FAMILY:IPR003660 , InterPro:IN-FAMILY:IPR004089 , InterPro:IN-FAMILY:IPR004090 , InterPro:IN-FAMILY:IPR004091 , Pfam:IN-FAMILY:PF00015 , Pfam:IN-FAMILY:PF00672 , Pfam:IN-FAMILY:PF02203 , Prints:IN-FAMILY:PR00260 , Prosite:IN-FAMILY:PS00538 , Prosite:IN-FAMILY:PS50111 , Prosite:IN-FAMILY:PS50885 , Smart:IN-FAMILY:SM00283 , Smart:IN-FAMILY:SM00304 , Smart:IN-FAMILY:SM00319
|Biological Process:||GO:0006935 - chemotaxis
[UniProtGOA11, GOA01, Manson86]
GO:0007165 - signal transduction [UniProtGOA11, GOA01]
|Molecular Function:||GO:0004871 - signal transducer activity
[UniProtGOA11, GOA01, Manson86]
GO:0004888 - transmembrane signaling receptor activity [GOA01, Manson86]
|Cellular Component:||GO:0005886 - plasma membrane
[UniProtGOA11a, UniProtGOA11, DiazMejia09, Zhang07, Daley05]
GO:0005887 - integral component of plasma membrane [Krikos83]
GO:0016020 - membrane [UniProtGOA11, GOA01]
GO:0016021 - integral component of membrane [UniProtGOA11, GOA01]
|MultiFun Terms:||cell processes → motility, chemotaxis, energytaxis (aerotaxis, redoxtaxis etc)|
|cell structure → membrane|
|regulation → type of regulation → posttranscriptional → inhibition / activation of enzymes|
|Growth Medium||Growth?||T (°C)||O2||pH||Osm/L||Growth Observations|
|LB enriched||Yes||37||Aerobic||6.95||Yes [Gerdes03, Comment 1]|
|LB Lennox||Yes||37||Aerobic||7||Yes [Baba06, Comment 2]|
|M9 medium with 1% glycerol||Yes||37||Aerobic||7.2||0.35||Yes [Joyce06, Comment 3]|
|MOPS medium with 0.4% glucose||Yes||37||Aerobic||7.2||0.22||Yes [Baba06, Comment 2]|
Subunit of: chemotaxis signaling complex - dipeptide sensing
Synonyms: MCP-IV chemotaxis signaling complex
Subunit composition of
chemotaxis signaling complex - dipeptide sensing = [(CheA)2][CheW]2[(Tap)2]3
CheA(L) histidine kinase = (CheA)2
methyl accepting chemotaxis protein - dipeptide sensing = (Tap)2 (extended summary available)
Chemotaxis in Escherichia coli is accomplished with a modified two-component signal transduction complex which transmits controlling signals to the flagellar motor complex. E.coli has four methyl-accepting chemotaxis protein (MCP)-type receptor complexes which recognize the following ligands: Tsr, serine;Tar, aspartate and maltose;Trg, ribose, galactose and glucose and Tap, dipeptides. Serine and aspartate bind directly to the receptor whereas maltose, ribose, galactose, glucose and dipeptides bind first to a periplasmic binding protein which then docks with its individual membrane receptor [Manson98].
The receptor complexes are ternary structures. The receptor-ligand interaction domain is located in the periplasm. Each receptor serves as the organizational framework for a receptor kinase signaling supermolecular complex formed in conjunction with histidine kinase CheA and other components of the signaling pathway [Falke97]. There are two transmembrane (TM) linker domains (CheW) which couple the methylation-dependent receptor to CheA. The receptors form homodimers with or without ligands [Gegner92]. CheA is a histidine kinase capable of autophosphorylation using ATP as a phosphodonor.The receptor complex dimers form trigonal units which in turn form a two-dimensional hexagonal lattice [Shimizu00] located usually at one pole of the cell. The Tsr and Tar receptors are the most abundant and the Tap, Trg receptors are less prevalent [Bren00].
CheA and CheY comprise a two-component signal transduction system where the signal is transmitted via phosphorylation from CheA to CheY (the response regulator). In several ways CheA/CheY differs from the standard two-component paradigm. Most significantly, CheY does not possess a DNA-binding domain and it doesn't act as a transcription factor. In the absence of activator ligand, CheA autophosphorylation is stimulated thus increasing the phosphotransfer from CheA to CheY, the messenger protein. CheY-P has a lower affinity for CheA than CheY, resulting in the dissociation of CheY-P from CheA. CheY-P has a higher affinity than CheY for the flagellar motor protein, FliM, a component of the motor supramolecular complex [Welch93a]. Binding of CheY to FliM increases the probability of flagellar rotation in the CW direction [Barak92a]. CCW rotation of the motor induces the flagellar filaments to coalesce into a bundle which propels the cell forward in a fairly straight line (run). CW rotation disrupts the bundle and causes the cell to tumble. The cell typically travels in a three-dimensional walk consisting of runs interspersed with random chaotic tumbling. CheZ is a cytosolic phosphatase which prevents overaccumulation of CheY-P by accelerating the decay of its aspartyl-phosphate residue [Hess87]. CheY-P is thus maintained during steady-state conditions at a level that generates the random walk [Manson98].
When an attractant molecule binds to the receptor, a conformational change is induced [Yeh93] which propagates across the membrane and results in a suppression of CheA autophosphorylation. Levels of CheY-P decrease and the cells tumble less frequently, causing an increase in their run lengths as they enter areas of higher attractant concentrations. The adaptation response is necessary, though, for the cells to respond properly to continually increasing attractant concentration. Adaptive methylation is carried out by two enzymes: the methyltransferase CheR and the methylesterase CheB [Toews79]. CheR is a constitutive enzyme which, through the use of S-adenosylmethionine, methylates glutamate residues in the cytoplasmic domains of the MCPs. CheB is a target for phosphotransfer from CheA, and the activated CheB-P functions as a methyl esterase which removes methyl groups from the MCPs, reducing their kinase activity. Under steady-state conditions, the addition of methyl groups by CheR is balanced by the methyl group removal by CheB-P and an intermediate level of receptor methylation is maintained, resulting in run-tumble behavior of the cell. When an attractant binds to a receptor and inhibits CheA activity, the levels of CheB-P drop. The decrease is slower than that for CheY-P though, since CheB-P is not a phosphate donor to CheZ. The rising level of methyl esters eventually stimulate histidine kinase activity and therefore counteract the effect of attractant binding to the receptor. This resets the receptor signal to its basal level [Falke97].
The components of the chemotaxis sensory system are arranged at one of the cell poles in tight clusters containing thousands of copies of each protein [Sourjik00]. Binding of an attractant results in an increase in the probability that CheA is inactive (unphosphorylated) and methylation of CheA on four specific glutamate residues increases the probability that that it is active (phosphorylated) [Borkovich92]. Lower levels of methylation reduce the activity of CheA but increase the affinity of the receptor for its attractant ligand [Li00].
|Transmembrane-Region||7 -> 33|
|Transmembrane-Region||189 -> 209|
|Conserved-Region||212 -> 264|
|Conserved-Region||269 -> 498|
|Sequence-Conflict||527 -> 533|
10/20/97 Gene b1885 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10987; confirmed by SwissProt match.
Abouhamad91: Abouhamad WN, Manson M, Gibson MM, Higgins CF (1991). "Peptide transport and chemotaxis in Escherichia coli and Salmonella typhimurium: characterization of the dipeptide permease (Dpp) and the dipeptide-binding protein." Mol Microbiol 5(5);1035-47. PMID: 1956284
Alexander07: Alexander RP, Zhulin IB (2007). "Evolutionary genomics reveals conserved structural determinants of signaling and adaptation in microbial chemoreceptors." Proc Natl Acad Sci U S A 104(8);2885-90. PMID: 17299051
Baba06: Baba T, Ara T, Hasegawa M, Takai Y, Okumura Y, Baba M, Datsenko KA, Tomita M, Wanner BL, Mori H (2006). "Construction of Escherichia coli K-12 in-frame, single-gene knockout mutants: the Keio collection." Mol Syst Biol 2;2006.0008. PMID: 16738554
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Falke97: Falke JJ, Bass RB, Butler SL, Chervitz SA, Danielson MA (1997). "The two-component signaling pathway of bacterial chemotaxis: a molecular view of signal transduction by receptors, kinases, and adaptation enzymes." Annu Rev Cell Dev Biol 13;457-512. PMID: 9442881
Gegner92: Gegner JA, Graham DR, Roth AF, Dahlquist FW (1992). "Assembly of an MCP receptor, CheW, and kinase CheA complex in the bacterial chemotaxis signal transduction pathway." Cell 70(6);975-82. PMID: 1326408
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
Hazelbauer81a: Hazelbauer GL, Engstrom P (1981). "Multiple forms of methyl-accepting chemotaxis proteins distinguished by a factor in addition to multiple methylation." J Bacteriol 145(1);35-42. PMID: 7007319
Joyce06: Joyce AR, Reed JL, White A, Edwards R, Osterman A, Baba T, Mori H, Lesely SA, Palsson BO, Agarwalla S (2006). "Experimental and computational assessment of conditionally essential genes in Escherichia coli." J Bacteriol 188(23);8259-71. PMID: 17012394
Kundu97: Kundu TK, Kusano S, Ishihama A (1997). "Promoter selectivity of Escherichia coli RNA polymerase sigmaF holoenzyme involved in transcription of flagellar and chemotaxis genes." J Bacteriol 179(13);4264-9. PMID: 9209042
Shimizu00: Shimizu TS, Le Novere N, Levin MD, Beavil AJ, Sutton BJ, Bray D (2000). "Molecular model of a lattice of signalling proteins involved in bacterial chemotaxis." Nat Cell Biol 2(11);792-6. PMID: 11056533
Toews79: Toews ML, Goy MF, Springer MS, Adler J (1979). "Attractants and repellents control demethylation of methylated chemotaxis proteins in Escherichia coli." Proc Natl Acad Sci U S A 76(11);5544-8. PMID: 392505
Welch93a: Welch M, Oosawa K, Aizawa S, Eisenbach M (1993). "Phosphorylation-dependent binding of a signal molecule to the flagellar switch of bacteria." Proc Natl Acad Sci U S A 90(19);8787-91. PMID: 8415608
Yeh93: Yeh JI, Biemann HP, Pandit J, Koshland DE, Kim SH (1993). "The three-dimensional structure of the ligand-binding domain of a wild-type bacterial chemotaxis receptor. Structural comparison to the cross-linked mutant forms and conformational changes upon ligand binding." J Biol Chem 268(13);9787-92. PMID: 8486661
Zhang07: Zhang N, Chen R, Young N, Wishart D, Winter P, Weiner JH, Li L (2007). "Comparison of SDS- and methanol-assisted protein solubilization and digestion methods for Escherichia coli membrane proteome analysis by 2-D LC-MS/MS." Proteomics 7(4);484-93. PMID: 17309111
Constantinidou06: Constantinidou C, Hobman JL, Griffiths L, Patel MD, Penn CW, Cole JA, Overton TW (2006). "A reassessment of the FNR regulon and transcriptomic analysis of the effects of nitrate, nitrite, NarXL, and NarQP as Escherichia coli K12 adapts from aerobic to anaerobic growth." J Biol Chem 281(8);4802-15. PMID: 16377617
Helmann87: Helmann JD, Chamberlin MJ (1987). "DNA sequence analysis suggests that expression of flagellar and chemotaxis genes in Escherichia coli and Salmonella typhimurium is controlled by an alternative sigma factor." Proc Natl Acad Sci U S A 84(18);6422-4. PMID: 3306678
Liu95: Liu X, Matsumura P (1995). "An alternative sigma factor controls transcription of flagellar class-III operons in Escherichia coli: gene sequence, overproduction, purification and characterization." Gene 164(1);81-4. PMID: 7590326
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