| Positions of β2 and β3 subunits in the large-conductance calcium- and voltage-activated BK potassium channel. | |
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MedLine Citation:
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PMID: 23277477 Owner: NLM Status: In-Data-Review |
Abstract/OtherAbstract:
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Large-conductance voltage- and Ca(2+)-gated K(+) channels are negative-feedback regulators of excitability in many cell types. They are complexes of α subunits and of one of four types of modulatory β subunits. These have intracellular N- and C-terminal tails and two transmembrane (TM) helices, TM1 and TM2, connected by an ∼100-residue extracellular loop. Based on endogenous disulfide formation between engineered cysteines (Cys), we found that in β2 and β3, as in β1 and β4, TM1 is closest to αS1 and αS2 and TM2 is closest to αS0. Mouse β3 (mβ3) has seven Cys in its loop, one of which is free, and this Cys readily forms disulfides with Cys substituted in the extracellular flanks of each of αS0-αS6. We identified by elimination mβ3-loop Cys152 as the only free Cys. We inferred the disulfide-bonding pattern of the other six Cys. Using directed proteolysis and fragment sizing, we determined this pattern first among the four loop Cys in β1. These are conserved in β2-β4, which have four additional Cys (eight in total), except that mβ3 has one fewer. In β1, disulfides form between Cys at aligned positions 1 and 8 and between Cys at aligned positions 5 and 6. In mβ3, the free Cys is at position 7; position 2 lacks a Cys present in all other β2-β4; and the disulfide pattern is 1-8, 3-4, and 5-6. Presumably, Cys 2 cross-links to Cys 7 in all other β2-β4. Cross-linking of mβ3 Cys152 to Cys substituted in the flanks of αS0-S5 attenuated the protection against iberiotoxin (IbTX); cross-linking of Cys152 to K296C in the αS6 flank and close to the pore enhanced protection against IbTX. In no case was N-type inactivation by the N-terminal tail of mβ3 perturbed. Although the mβ3 loop can move, its position with Cys152 near αK296, in which it blocks IbTX binding, is likely favored. |
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Authors:
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Roland S Wu; Guoxia Liu; Sergey I Zakharov; Neelesh Chudasama; Howard Motoike; Arthur Karlin; Steven O Marx |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: The Journal of general physiology Volume: 141 ISSN: 1540-7748 ISO Abbreviation: J. Gen. Physiol. Publication Date: 2013 Jan |
Date Detail:
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Created Date: 2013-01-01 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985110R Medline TA: J Gen Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 105-17 Citation Subset: IM |
Affiliation:
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Division of Cardiology, Department of Medicine, 2 Center for Molecular Recognition, 3 Department of Biochemistry, 4 Department of Physiology, 5 Department of Neurology, and 6 Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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