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Escherichia coli K-12 substr. MG1655 Transporter: potassium dependent mechanosensitive channel MscK

Gene: mscK Accession Numbers: G6255 (EcoCyc), b0465, ECK0459

Synonyms: aefA, kefA

Regulation Summary Diagram: ?

Regulation summary diagram for mscK

MscK, the potassium-dependent mechanosensitive (MS) channel of small conductance, is one of four classes of E.coli MS channels. Another is MscS (MS channel of small conductance) which exhibits an activity which is below that of MscL (MS channel of large conductance) and above that of MscM (MS channel of mini conductance). Mutation, deletion, and complementation studies using patch clamp conductance measurements have characterized two E.coli genes that are required for MscS activity: yggB and kefA. Deletion of yggB in kefA-deletion mutants eliminates all MscS activity and complementation with YggB on a moderate copy number plasmid restores MscS activity. Studies on mutants lacking YggB but possessing MscK exhibited a lesser amount of patch current activity but this activity did not desensitize and the duration of this activity was longer than that seen in YggB-encoded MscS activity. The results of the study suggest that kefA codes for a MS channel with similar conductance characteristics as MscS but which does not desensitize upon extended pressure [Levina99]. A gain-of-function MscK mutant failed to grow in media containing high levels of potassium due to an inability to regulate cell potassium [McLaggan02]. Patch-clamp experiments reveal MscK gates at lower membrane tensions than MscS, and that only potassium on the periplasmic side of the membrane is important for MscK gating, though sodium passes as easily as potassium through the channel once it is opened. Ammonium, rubidium, and cesium are also able to activate MscK activity in addition to potassium [Li02]. Expression of the C-terminal domain of MscK (predicted to be the channel-containing domain) resulted in increased survival of mscL mscS mscK mutants [Miller03].

Protein fusion experiments with MscK reveal the protein has a N-terminal periplasmic domain, an 11 transmembrane-segment inner membrane domain, a C-terminal cytoplasmic domain, and a signal sequence of 33 amino acids [McLaggan02].

There are two classes of KefA/YggB homologs: large proteins (700 residues or larger) and smaller proteins (300-500 residues). The large KefA homologs have thus far only been found in Gram-negative bacteria while the small KefA homologs are widespread in bacterial genomes. E. coli has three members of the large KefA family (KefA, YjeP and YbiO and two members of the smaller homologs (YggB and YnaI). The remaining homologs (Yjep, YnaI and YbiO) do not exhibit deletion mutants of detectable phenotype [Levina99].

Seven mechanosensitive ion channels have been characterised in E. coli K-12: MscL, MscS, MscK, MscM, YnaI, YbiO and YbdG. A strain lacking all seven of these proteins fails to demonstrate channel opening in patch clamp experiments [Edwards12].

Citations: [Li07, Akitake05, Cui96, Cui95]

Locations: inner membrane

Map Position: [485,760 -> 489,122] (10.47 centisomes, 38°)
Length: 3363 bp / 1120 aa

Molecular Weight of Polypeptide: 127.22 kD (from nucleotide sequence)

Unification Links: ASAP:ABE-0001613 , DIP:DIP-10070N , EchoBASE:EB3991 , EcoGene:EG14240 , EcoliWiki:b0465 , ModBase:P77338 , OU-Microarray:b0465 , PortEco:kefA , PR:PRO_000023060 , Pride:P77338 , Protein Model Portal:P77338 , RefSeq:NP_414998 , RegulonDB:G6255 , SMR:P77338 , String:511145.b0465 , UniProt:P77338

Relationship Links: InterPro:IN-FAMILY:IPR006685 , InterPro:IN-FAMILY:IPR006686 , InterPro:IN-FAMILY:IPR010920 , InterPro:IN-FAMILY:IPR011014 , InterPro:IN-FAMILY:IPR011066 , InterPro:IN-FAMILY:IPR024393 , InterPro:IN-FAMILY:IPR025692 , Pfam:IN-FAMILY:PF00924 , Pfam:IN-FAMILY:PF12794 , Pfam:IN-FAMILY:PF12795 , Prosite:IN-FAMILY:PS01246

In Paralogous Gene Group: 133 (3 members)

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Biological Process: GO:0009992 - cellular water homeostasis Inferred from experiment [McLaggan02]
GO:0006810 - transport Inferred by computational analysis [UniProtGOA11]
GO:0006811 - ion transport Inferred by computational analysis [UniProtGOA11]
GO:0006813 - potassium ion transport Inferred by computational analysis [UniProtGOA11]
GO:0055085 - transmembrane transport Inferred by computational analysis [GOA01]
GO:0071470 - cellular response to osmotic stress Inferred by computational analysis [Gaudet10]
Molecular Function: GO:0008381 - mechanically-gated ion channel activity Inferred from experiment [Levina99]
Cellular Component: GO:0005886 - plasma membrane Inferred from experiment Inferred by computational analysis [UniProtGOA11a, UniProtGOA11, DiazMejia09, Zhang07, Daley05, Berrier89]
GO:0016020 - membrane Inferred by computational analysis [UniProtGOA11, GOA01]
GO:0016021 - integral component of membrane Inferred by computational analysis [UniProtGOA11]

MultiFun Terms: cell processes adaptations other (mechanical, nutritional, oxidative stress)
cell structure membrane
transport Channel-type Transporters alpha-type channels

Essentiality data for mscK knockouts: ?

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]

Last-Curated ? 11-Oct-2007 by Johnson A , JCVI

Enzymatic reaction of: KefA (potassium dependent mechanosensitive channel MscK)

Transport reaction diagram for KefA

Sequence Features

Protein sequence of potassium dependent mechanosensitive channel MscK with features indicated

Feature Class Location Citations Comment
Signal-Sequence 1 -> 33
Chain 34 -> 1120
UniProt: Potassium efflux system kefA;
Transmembrane-Region 500 -> 520
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 561 -> 581
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 583 -> 603
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 635 -> 655
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 658 -> 678
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 693 -> 713
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 729 -> 749
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 797 -> 817
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 840 -> 860
UniProt: Helical;; Non-Experimental Qualifier: potential;
Transmembrane-Region 887 -> 907
UniProt: Helical;; Non-Experimental Qualifier: potential;
Mutagenesis-Variant 922
[McLaggan02, UniProt15]
UniProt: Prevents growth in medium containing high levels of potassium in the presence of betaine.
Transmembrane-Region 922 -> 942
UniProt: Helical;; Non-Experimental Qualifier: potential;

Gene Local Context (not to scale): ?

Gene local context diagram

Transcription Unit:

Transcription-unit diagram


Markus Krummenacker on Tue Oct 14, 1997:
Gene object created from Blattner lab Genbank (v. M52) entry.


Akitake05: Akitake B, Anishkin A, Sukharev S (2005). "The "dashpot" mechanism of stretch-dependent gating in MscS." J Gen Physiol 125(2);143-54. PMID: 15657299

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

Berrier89: Berrier C, Coulombe A, Houssin C, Ghazi A (1989). "A patch-clamp study of ion channels of inner and outer membranes and of contact zones of E. coli, fused into giant liposomes. Pressure-activated channels are localized in the inner membrane." FEBS Lett 259(1);27-32. PMID: 2480919

Cui95: Cui C, Smith DO, Adler J (1995). "Characterization of mechanosensitive channels in Escherichia coli cytoplasmic membrane by whole-cell patch clamp recording." J Membr Biol 144(1);31-42. PMID: 7595939

Cui96: Cui C, Adler J (1996). "Effect of mutation of potassium-efflux system, KefA, on mechanosensitive channels in the cytoplasmic membrane of Escherichia coli." J Membr Biol 150(2);143-52. PMID: 8661775

Daley05: Daley DO, Rapp M, Granseth E, Melen K, Drew D, von Heijne G (2005). "Global topology analysis of the Escherichia coli inner membrane proteome." Science 308(5726);1321-3. PMID: 15919996

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

Edwards12: Edwards MD, Black S, Rasmussen T, Rasmussen A, Stokes NR, Stephen TL, Miller S, Booth IR (2012). "Characterization of three novel mechanosensitive channel activities in Escherichia coli." Channels (Austin) 6(4);272-81. PMID: 22874652

Gaudet10: Gaudet P, Livstone M, Thomas P (2010). "Annotation inferences using phylogenetic trees." PMID: 19578431

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

GOA01: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

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

Levina99: Levina N, Totemeyer S, Stokes NR, Louis P, Jones MA, Booth IR (1999). "Protection of Escherichia coli cells against extreme turgor by activation of MscS and MscL mechanosensitive channels: identification of genes required for MscS activity." EMBO J 1999;18(7);1730-7. PMID: 10202137

Li02: Li Y, Moe PC, Chandrasekaran S, Booth IR, Blount P (2002). "Ionic regulation of MscK, a mechanosensitive channel from Escherichia coli." EMBO J 21(20);5323-30. PMID: 12374733

Li07: Li C, Edwards MD, Jeong H, Roth J, Booth IR (2007). "Identification of mutations that alter the gating of the Escherichia coli mechanosensitive channel protein, MscK." Mol Microbiol 64(2);560-74. PMID: 17493135

Linton02: Linton D, Allan E, Karlyshev AV, Cronshaw AD, Wren BW (2002). "Identification of N-acetylgalactosamine-containing glycoproteins PEB3 and CgpA in Campylobacter jejuni." Mol Microbiol 43(2);497-508. PMID: 11985725

McLaggan02: McLaggan D, Jones MA, Gouesbet G, Levina N, Lindey S, Epstein W, Booth IR (2002). "Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli." Mol Microbiol 43(2);521-36. PMID: 11985727

Miller03: Miller S, Bartlett W, Chandrasekaran S, Simpson S, Edwards M, Booth IR (2003). "Domain organization of the MscS mechanosensitive channel of Escherichia coli." EMBO J 22(1);36-46. PMID: 12505982

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

UniProt10: UniProt Consortium (2010). "UniProt version 2010-07 released on 2010-06-15 00:00:00." Database.

UniProt15: UniProt Consortium (2015). "UniProt version 2015-01 released on 2015-01-16 00:00:00." Database.

UniProtGOA11: UniProt-GOA (2011). "Gene Ontology annotation based on manual assignment of UniProtKB keywords in UniProtKB/Swiss-Prot entries."

UniProtGOA11a: UniProt-GOA (2011). "Gene Ontology annotation based on the manual assignment of UniProtKB Subcellular Location terms in UniProtKB/Swiss-Prot entries."

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

Other References Related to Gene Regulation

MendozaVargas09: Mendoza-Vargas A, Olvera L, Olvera M, Grande R, Vega-Alvarado L, Taboada B, Jimenez-Jacinto V, Salgado H, Juarez K, Contreras-Moreira B, Huerta AM, Collado-Vides J, Morett E (2009). "Genome-wide identification of transcription start sites, promoters and transcription factor binding sites in E. coli." PLoS One 4(10);e7526. PMID: 19838305

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
Page generated by SRI International Pathway Tools version 19.0 on Fri Aug 28, 2015, BIOCYC14B.