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1.A.1.13.2
2 TMS ( P-loop) Ca2+-gated K+ channel, MthK (see Jiang et al., 2002 for the crystal structure, and Parfenova et al., 2006 for mutations affecting open probability). For the studies of ion permeation and Ca2+ blockage, see Derebe et al., 2011. (structures: 3LDD_A and 2OGU_A.). Voltage-dependent K+ channels including MthK which lacks a canonical voltage sensor can undergo a gating process known as C-type inactivation, which involves entry into a nonconducting state through conformational changes near the channel's selectivity filter (Thomson and Rothberg, 2010). C-type inactivation may involve movements of transmembrane voltage sensor domains. In the absence of Ca2+, a single structure in a closed state was observed by cryoEM that was highly flexible with large rocking motions of the gating ring and bending of pore-lining helices (Fan et al. 2020). In Ca2+-bound conditions, several open-inactivated conformations were present with the different channel conformations being distinguished by rocking of the gating rings with respect to the transmembrane region. In all conformations displaying open channel pores, the N-terminus of one subunit of the channel tetramer sticks into the pore and plugs it. Deletion of this N terminus led to non-inactivating channels with structures of open states without a pore plug, indicating that this N-terminal peptide is responsible for a ball-and-chain inactivation mechanism (Fan et al. 2020). Lipid-protein interactions influence the conformational equilibrium between two states of the channel that differ according to whether a TMS has a kink. Two key residues in the kink region mediate crosstalk between two gates at the selectivity filter and the central cavity, respectively. Opening of one gate eventually leads to closure of the other (Gu and de Groot 2020). Activation of MthK is exquisitely regulated by temperature (Jiang et al. 2020).  

Accession Number:O27564
Protein Name:Calcium-gated potassium channel MthK
Length:336
Molecular Weight:37314.00
Species:Methanobacterium thermoautotrophicum [187420]
Number of TMSs:2
Location1 / Topology2 / Orientation3: Cell membrane1 / Multi-pass membrane protein2
Substrate K+

Cross database links:

DIP: DIP-46253N
RefSeq: NP_276634.1   
Entrez Gene ID: 1471789   
Pfam: PF07885    PF02080    PF02254   
BioCyc: MTHE187420:MTH1520-MONOMER   
KEGG: mth:MTH1520   

Gene Ontology

GO:0016021 C:integral to membrane
GO:0005886 C:plasma membrane
GO:0003824 F:catalytic activity
GO:0008324 F:cation transmembrane transporter activity
GO:0005216 F:ion channel activity
GO:0046872 F:metal ion binding
GO:0008152 P:metabolic process
GO:0006813 P:potassium ion transport

References (2)

[1] “Complete genome sequence of Methanobacterium thermoautotrophicum deltaH: functional analysis and comparative genomics.”  Smith D.R.et.al.   9371463
[2] “Crystal structure and mechanism of a calcium-gated potassium channel.”  Jiang Y.et.al.   12037559
Structure:
1LNQ   2AEF   2AEJ   2AEM   2FY8   2OGU   3KXD   3LDC   3LDD   3LDE   [...more]

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MVLVIEIIRK HLPRVLKVPA TRILLLVLAV IIYGTAGFHF IEGESWTVSL YWTFVTIATV 
61:	GYGDYSPSTP LGMYFTVTLI VLGIGTFAVA VERLLEFLIN REQMKLMGLI DVAKSRHVVI 
121:	CGWSESTLEC LRELRGSEVF VLAEDENVRK KVLRSGANFV HGDPTRVSDL EKANVRGARA 
181:	VIVDLESDSE TIHCILGIRK IDESVRIIAE AERYENIEQL RMAGADQVIS PFVISGRLMS 
241:	RSIDDGYEAM FVQDVLAEES TRRMVEVPIP EGSKLEGVSV LDADIHDVTG VIIIGVGRGD 
301:	ELIIDPPRDY SFRAGDIILG IGKPEEIERL KNYISA