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1.A.1.3.10
Calcium-, magnesium- and voltage-activated K+ channel, Slo1 (Kcma1; KCNMA), a BK channel, of 1236 aas and 6 N-terminal TMSs. Its activation dampens the excitatory events that elevate the cytosolic Ca2+ concentration and/or depolarize the cell membrane. It therefore contributes to repolarization of the membrane potential, and it plays a key role in controlling excitability in a number of systems. Ethanol and carbon monoxide-bound heme increase channel activation while heme inhibits channel activation (Tang et al. 2003). The molecular structures of the human Slo1 channel in complex with beta4 has been solved revealing four beta4 subunits, each containing two transmembrane helices, encircling Slo1, contacting it through helical interactions inside the membrane. On the extracellular side, beta4 forms a tetrameric crown over the pore. Structures with high and low Ca2+ concentrations show that identical gating conformations occur in the absence and presence of beta4, implying that beta4 serves to modulate the relative stabilities of 'pre-existing' conformations rather than creating new ones (Tao and MacKinnon 2019). BK channels show increased activities in Angelman syndrome due to genetic defects in the ubiquitin protein ligase E3A (UBE3A) gene (Sun et al. 2019). It is a large-conductance potassium (BK) channel that can be synergistically and independently activated by membrane voltage and intracellular Ca2+. The only covalent connection between the cytosolic Ca2+-sensing domain and the TM pore and voltage sensing domains is a 15-residue 'C-linker' which plays a direct role in mediating allosteric coupling between BK domains (Yazdani et al. 2020).  

Accession Number:Q12791
Protein Name:Calcium-activated potassium channel subunit alpha-1
Length:1236
Molecular Weight:137560.00
Species:Homo sapiens (Human) [9606]
Number of TMSs:7
Location1 / Topology2 / Orientation3: Cell membrane1 / Multi-pass membrane protein2
Substrate

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FASTA formatted sequence
1:	MANGGGGGGG SSGGGGGGGG SSLRMSSNIH ANHLSLDASS SSSSSSSSSS SSSSSSSSSS 
61:	VHEPKMDALI IPVTMEVPCD SRGQRMWWAF LASSMVTFFG GLFIILLWRT LKYLWTVCCH 
121:	CGGKTKEAQK INNGSSQADG TLKPVDEKEE AVAAEVGWMT SVKDWAGVMI SAQTLTGRVL 
181:	VVLVFALSIG ALVIYFIDSS NPIESCQNFY KDFTLQIDMA FNVFFLLYFG LRFIAANDKL 
241:	WFWLEVNSVV DFFTVPPVFV SVYLNRSWLG LRFLRALRLI QFSEILQFLN ILKTSNSIKL 
301:	VNLLSIFIST WLTAAGFIHL VENSGDPWEN FQNNQALTYW ECVYLLMVTM STVGYGDVYA 
361:	KTTLGRLFMV FFILGGLAMF ASYVPEIIEL IGNRKKYGGS YSAVSGRKHI VVCGHITLES 
421:	VSNFLKDFLH KDRDDVNVEI VFLHNISPNL ELEALFKRHF TQVEFYQGSV LNPHDLARVK 
481:	IESADACLIL ANKYCADPDA EDASNIMRVI SIKNYHPKIR IITQMLQYHN KAHLLNIPSW 
541:	NWKEGDDAIC LAELKLGFIA QSCLAQGLST MLANLFSMRS FIKIEEDTWQ KYYLEGVSNE 
601:	MYTEYLSSAF VGLSFPTVCE LCFVKLKLLM IAIEYKSANR ESRILINPGN HLKIQEGTLG 
661:	FFIASDAKEV KRAFFYCKAC HDDITDPKRI KKCGCKRPKM SIYKRMRRAC CFDCGRSERD 
721:	CSCMSGRVRG NVDTLERAFP LSSVSVNDCS TSFRAFEDEQ PSTLSPKKKQ RNGGMRNSPN 
781:	TSPKLMRHDP LLIPGNDQID NMDSNVKKYD STGMFHWCAP KEIEKVILTR SEAAMTVLSG 
841:	HVVVCIFGDV SSALIGLRNL VMPLRASNFH YHELKHIVFV GSIEYLKREW ETLHNFPKVS 
901:	ILPGTPLSRA DLRAVNINLC DMCVILSANQ NNIDDTSLQD KECILASLNI KSMQFDDSIG 
961:	VLQANSQGFT PPGMDRSSPD NSPVHGMLRQ PSITTGVNIP IITELVNDTN VQFLDQDDDD 
1021:	DPDTELYLTQ PFACGTAFAV SVLDSLMSAT YFNDNILTLI RTLVTGGATP ELEALIAEEN 
1081:	ALRGGYSTPQ TLANRDRCRV AQLALLDGPF ADLGDGGCYG DLFCKALKTY NMLCFGIYRL 
1141:	RDAHLSTPSQ CTKRYVITNP PYEFELVPTD LIFCLMQFDH NAGQSRASLS HSSHSSQSSS 
1201:	KKSSSVHSIP STANRQNRPK SRESRDKQKY VQEERL