|
|
|
|
|
|
|
||
An Essential Role of a Terminal Peptide Segment of Three Hydrophobic Residues
2 Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110
Address correspondence to C. Lingle, Department of Anesthesiology, Washington University School of Medicine, 600 S. Euclid Ave., Box 8054, St. Louis, MO 63110. Fax: (314) 362-8571; E-mail: clingle{at}morpheus.wustl.edu
An auxiliary ß2 subunit, when coexpressed with Slo 
subunits, produces inactivation of the resulting large-conductance, Ca2+ and voltage-dependent K+ (BK-type) channels. Inactivation is mediated by the cytosolic NH2 terminus of the ß2 subunit. To understand the structural requirements for inactivation, we have done a mutational analysis of the role of the NH2 terminus in the inactivation process. The ß2 NH2 terminus contains 46 residues thought to be cytosolic to the first transmembrane segment (TM1). Here, we address two issues. First, we define the key segment of residues that mediates inactivation. Second, we examine the role of the linker between the inactivation segment and TM1. The results show that the critical determinant for inactivation is an initial segment of three amino acids (residues 2–4: FIW) after the initiation methionine. Deletions that scan positions from residue 5 through residue 36 alter inactivation, but do not abolish it. In contrast, deletion of FIW or combinations of point mutations within the FIW triplet abolish inactivation. Mutational analysis of the three initial residues argues that inactivation does not result from a well-defined structure formed by this epitope. Inactivation may be better explained by linear entry of the NH2-terminal peptide segment into the permeation pathway with residue hydrophobicity and size influencing the onset and recovery from inactivation. Examination of the ability of artificial, polymeric linkers to support inactivation suggests that a variety of amino acid sequences can serve as adequate linkers as long as they contain a minimum of 12 residues between the first transmembrane segment and the FIW triplet. Thus, neither a specific distribution of charge on the linker nor a specific structure in the linker is required to support the inactivation process.
Key Words: inactivation mechanisms • inactivation domains • K+ channels • BK channels • Ca2+- and voltage-gated K+ channels
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  H. Zeng, E. Gordon, Z. Lin, I. M. Lozinskaya, R. N. Willette, and X. Xu 1-[1-Hexyl-6-(methyloxy)-1H-indazol-3-yl]-2-methyl-1-propanone, a Potent and Highly Selective Small Molecule Blocker of the Large-Conductance Voltage-Gated and Calcium-Dependent K+ Channel J. Pharmacol. Exp. Ther., October 1, 2008; 327(1): 168 - 177. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Liu, S. I. Zakharov, L. Yang, R. S. Wu, S.-X. Deng, D. W. Landry, A. Karlin, and S. O. Marx Locations of the {beta}1 transmembrane helices in the BK potassium channel PNAS, August 5, 2008; 105(31): 10727 - 10732. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Zeng, X.-M. Xia, and C. J. Lingle Species-specific Differences among KCNMB3 BK {beta}3 Auxiliary Subunits: Some {beta}3 N-terminal Variants May Be Primate-specific Subunits J. Gen. Physiol., July 1, 2008; 132(1): 115 - 129. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Yang, G. Zhang, J. Shi, U. S. Lee, K. Delaloye, and J. Cui Subunit-Specific Effect of the Voltage Sensor Domain on Ca2+ Sensitivity of BK Channels Biophys. J., June 15, 2008; 94(12): 4678 - 4687. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Lv, M. Chen, G. Gan, L. Wang, T. Xu, and J. Ding Four-turn {alpha}-Helical Segment Prevents Surface Expression of the Auxiliary h{beta}2 Subunit of BK-type Channel J. Biol. Chem., February 1, 2008; 283(5): 2709 - 2715. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. P. Torres, F. J. Morera, I. Carvacho, and R. Latorre A Marriage of Convenience: beta-Subunits and Voltage-dependent K+ Channels J. Biol. Chem., August 24, 2007; 282(34): 24485 - 24489. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Li, J. Yao, X. Tong, Z. Guo, Y. Wu, L. Sun, N. Pan, H. Wu, T. Xu, and J. Ding Interaction Sites between the Slo1 Pore and the NH2 Terminus of the beta2 Subunit, Probed with a Three-residue Sensor J. Biol. Chem., June 15, 2007; 282(24): 17720 - 17728. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Zhang, Y. Zhou, J.-P. Ding, X.-M. Xia, and C. J. Lingle A Limited Access Compartment between the Pore Domain and Cytosolic Domain of the BK Channel. J. Neurosci., November 15, 2006; 26(46): 11833 - 11843. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Zeng, T. M. Weiger, H. Fei, and I. B. Levitan Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel J. Gen. Physiol., November 1, 2006; 128(5): 583 - 591. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Li and R. W. Aldrich State-dependent Block of BK Channels by Synthesized Shaker Ball Peptides J. Gen. Physiol., October 1, 2006; 128(4): 423 - 441. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. T. King, P. V. Lovell, M. Rishniw, M. I. Kotlikoff, M. L. Zeeman, and D. P. McCobb beta2 and beta4 Subunits of BK Channels Confer Differential Sensitivity to Acute Modulation by Steroid Hormones J Neurophysiol, May 1, 2006; 95(5): 2878 - 2888. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. R. Benzinger, X.-M. Xia, and C. J. Lingle Direct Observation of a Preinactivated, Open State in BK Channels with {beta}2 Subunits J. Gen. Physiol., January 30, 2006; 127(2): 119 - 131. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Zeng, T. M. Weiger, H. Fei, A. M. Jaramillo, and I. B. Levitan The Amino Terminus of Slob, Slowpoke Channel Binding Protein, Critically Influences Its Modulation of the Channel J. Gen. Physiol., May 31, 2005; 125(6): 631 - 640. [Abstract] [Full Text] [PDF]
|
|
|
|
