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1.A.1.7.1
Tok1 twin (dual) barrel outward rectifying K+ channel with exterme assymmetry which includes an extra 4 N-terminal TMSs for a total of 16 TMSs.  (Transports K+ and Cs+) (Bertl et al., 2003; Roller et al. 2008).  TOKs are outwardly rectifying K+ channels in fungi with two pore-loops and eight transmembrane spans. Lewis et al. 2020 described the TOKs from four fungal pathogens. These TOKs pass large currents only in the outward direction like this ScTOK. ScTOK, AfTOK1 (Aspergillus fumigatus), and H99TOK (Cryptococcus neoformans grubii) are K+-selective and pass current above the K+ reversal potential. CaTOK (Candida albicans) and CnTOK (Cryptococcus neoformans neoformans) pass both K+ and Na+ and conduct above a reversal potential, reflecting the mixed permeability of their selectivity filter. Mutations in CaTOK and ScTOK at sites homologous to those that open the internal gates in classical K+ channels are shown to produce inward TOK currents. Possibly the reversal potential determines ion occupancy, and thus, conductivity, of the selectivity filter gate that is coupled to an imperfectly restrictive internal gate, permitting the filter to sample ion concentrations on both sides of the membrane (Lewis et al. 2020).

Accession Number:P40310
Protein Name:TOK1 aka DUK1 aka YJL093C aka J0911
Length:691
Molecular Weight:77408.00
Species:Saccharomyces cerevisiae (Baker's yeast) [4932]
Number of TMSs:9
Location1 / Topology2 / Orientation3: Membrane1 / Multi-pass membrane protein2
Substrate K+

Cross database links:

DIP: DIP-8165N
RefSeq: NP_012442.1   
Entrez Gene ID: 853352   
Pfam: PF07885   
KEGG: sce:YJL093C   

Gene Ontology

GO:0016021 C:integral to membrane
GO:0005886 C:plasma membrane
GO:0005267 F:potassium channel activity
GO:0005244 F:voltage-gated ion channel activity
GO:0030007 P:cellular potassium ion homeostasis
GO:0006813 P:potassium ion transport

References (7)

[1] “A new family of outwardly rectifying potassium channel proteins with two pore domains in tandem.”  Ketchum K.A.et.al.   7651518
[2] “The S. cerevisiae outwardly-rectifying potassium channel (DUK1) identifies a new family of channels with duplicated pore domains.”  Reid J.D.et.al.   8723646
[3] “A pH-sensitive yeast outward rectifier K+ channel with two pore domains and novel gating properties.”  Lesage F.et.al.   8626760
[4] “Sequence and function analysis of a 9.46 kb fragment of Saccharomyces cerevisiae chromosome X.”  Miosga T.et.al.   7985424
[5] “Complete nucleotide sequence of Saccharomyces cerevisiae chromosome X.”  Galibert F.et.al.   8641269
[6] “A global topology map of the Saccharomyces cerevisiae membrane proteome.”  Kim H.et.al.   16847258
[7] “A multidimensional chromatography technology for in-depth phosphoproteome analysis.”  Albuquerque C.P.et.al.   18407956

External Searches:

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MTRFMNSFAK QTLGYGNMAT VEQESSAQAV DSHSNNTPKQ AKGVLAEELK DALRFRDERV 
61:	SIINAEPSST LFVFWFVVSC YFPVITACLG PVANTISIAC VVEKWRSLKN NSVVTNPRSN 
121:	DTDVLMNQVK TVFDPPGIFA VNIISLVLGF TSNIILMLHF SKKLTYLKSQ LINITGWTIA 
181:	GGMLLVDVIV CSLNDMPSIY SKTIGFWFAC ISSGLYLVCT IILTIHFIGY KLGKYPPTFN 
241:	LLPNERSIMA YTVLLSLWLI WGAGMFSGLL HITYGNALYF CTVSLLTVGL GDILPKSVGA 
301:	KIMVLIFSLS GVVLMGLIVF MTRSIIQKSS GPIFFFHRVE KGRSKSWKHY MDSSKNLSER 
361:	EAFDLMKCIR QTASRKQHWF SLSVTIAIFM AFWLLGALVF KFAENWSYFN CIYFCFLCLL 
421:	TIGYGDYAPR TGAGRAFFVI WALGAVPLMG AILSTVGDLL FDISTSLDIK IGESFNNKVK 
481:	SIVFNGRQRA LSFMVNTGEI FEESDTADGD LEENTTSSQS SQISEFNDNN SEENDSGVTS 
541:	PPASLQESFS SLSKASSPEG ILPLEYVSSA EYALQDSGTC NLRNLQELLK AVKKLHRICL 
601:	ADKDYTLSFS DWSYIHKLHL RNITDIEEYT RGPEFWISPD TPLKFPLNEP HFAFMMLFKN 
661:	IEELVGNLVE DEELYKVISK RKFLGEHRKT L