A 59 amino acid insertion increases Ca2+ sensitivity of rbslo1, a Ca2+-activated K+ channel in renal epithelia

K. Hanaoka, J. M. Wright, I. B. Cheglakov, T. Morita, William B Guggino

Research output: Contribution to journalArticle

Abstract

We previously cloned a MaxiK channel α-subunit isoform, rbslo1, from rabbit kidney with an amino acid sequence highly homologous to mslo but with a 59 amino acid insertion between S8 and S9 (Morita et al., 1997. Am. J. Physiol. 273:F615-F624). rbslo1 activation properties differed substantially from mslo with much greater Ca2+ sensitivity, half-activation potential of -49 mV in 1 μM Ca2+. We now report single-channel analysis of rbslo1 and delA, a construct produced by removal of the 59 amino acid insertion at site A. delA is identical to mslo from upstream of S1 to downstream of S10 with the exception of 8 amino acids. Slope of the steady-state Boltzmann voltage activation curve was 8.1 mV per e-fold change in probability of opening for both rbslo1 and delA. The apparent [Ca2+](i) properties in delA were more like mslo but the voltage-activation properties remained distinctly rbslo1. Ca2+ affinity decreased and transmembrane voltage effects on apparent Ca2+ affinity increased in delA. The differences between rbslo1 and other cloned channels appear to be localized at insertion site A with both the insertion sequence and amino acid substitutions near site A being important. The steeper activation slope makes the channel more responsive to small changes in transmembrane voltage while the insertion sequence makes the channel functional at physiological low levels of [Ca2+](i).

Original languageEnglish (US)
Pages (from-to)193-201
Number of pages9
JournalJournal of Membrane Biology
Volume172
Issue number3
DOIs
StatePublished - 1999

Fingerprint

Calcium-Activated Potassium Channels
Epithelium
Insertional Mutagenesis
Kidney
Amino Acids
S 10
Large-Conductance Calcium-Activated Potassium Channels
Amino Acid Sequence Homology
Amino Acid Substitution
Protein Isoforms
Rabbits

Keywords

  • BK channel
  • Gating
  • Potassium channel
  • Single-channel recording

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

Cite this

A 59 amino acid insertion increases Ca2+ sensitivity of rbslo1, a Ca2+-activated K+ channel in renal epithelia. / Hanaoka, K.; Wright, J. M.; Cheglakov, I. B.; Morita, T.; Guggino, William B.

In: Journal of Membrane Biology, Vol. 172, No. 3, 1999, p. 193-201.

Research output: Contribution to journalArticle

Hanaoka, K. ; Wright, J. M. ; Cheglakov, I. B. ; Morita, T. ; Guggino, William B. / A 59 amino acid insertion increases Ca2+ sensitivity of rbslo1, a Ca2+-activated K+ channel in renal epithelia. In: Journal of Membrane Biology. 1999 ; Vol. 172, No. 3. pp. 193-201.
@article{537ed8b78ccb48838f62a1def08d6e9e,
title = "A 59 amino acid insertion increases Ca2+ sensitivity of rbslo1, a Ca2+-activated K+ channel in renal epithelia",
abstract = "We previously cloned a MaxiK channel α-subunit isoform, rbslo1, from rabbit kidney with an amino acid sequence highly homologous to mslo but with a 59 amino acid insertion between S8 and S9 (Morita et al., 1997. Am. J. Physiol. 273:F615-F624). rbslo1 activation properties differed substantially from mslo with much greater Ca2+ sensitivity, half-activation potential of -49 mV in 1 μM Ca2+. We now report single-channel analysis of rbslo1 and delA, a construct produced by removal of the 59 amino acid insertion at site A. delA is identical to mslo from upstream of S1 to downstream of S10 with the exception of 8 amino acids. Slope of the steady-state Boltzmann voltage activation curve was 8.1 mV per e-fold change in probability of opening for both rbslo1 and delA. The apparent [Ca2+](i) properties in delA were more like mslo but the voltage-activation properties remained distinctly rbslo1. Ca2+ affinity decreased and transmembrane voltage effects on apparent Ca2+ affinity increased in delA. The differences between rbslo1 and other cloned channels appear to be localized at insertion site A with both the insertion sequence and amino acid substitutions near site A being important. The steeper activation slope makes the channel more responsive to small changes in transmembrane voltage while the insertion sequence makes the channel functional at physiological low levels of [Ca2+](i).",
keywords = "BK channel, Gating, Potassium channel, Single-channel recording",
author = "K. Hanaoka and Wright, {J. M.} and Cheglakov, {I. B.} and T. Morita and Guggino, {William B}",
year = "1999",
doi = "10.1007/s002329900596",
language = "English (US)",
volume = "172",
pages = "193--201",
journal = "Journal of Membrane Biology",
issn = "0022-2631",
publisher = "Springer New York",
number = "3",

}

TY - JOUR

T1 - A 59 amino acid insertion increases Ca2+ sensitivity of rbslo1, a Ca2+-activated K+ channel in renal epithelia

AU - Hanaoka, K.

AU - Wright, J. M.

AU - Cheglakov, I. B.

AU - Morita, T.

AU - Guggino, William B

PY - 1999

Y1 - 1999

N2 - We previously cloned a MaxiK channel α-subunit isoform, rbslo1, from rabbit kidney with an amino acid sequence highly homologous to mslo but with a 59 amino acid insertion between S8 and S9 (Morita et al., 1997. Am. J. Physiol. 273:F615-F624). rbslo1 activation properties differed substantially from mslo with much greater Ca2+ sensitivity, half-activation potential of -49 mV in 1 μM Ca2+. We now report single-channel analysis of rbslo1 and delA, a construct produced by removal of the 59 amino acid insertion at site A. delA is identical to mslo from upstream of S1 to downstream of S10 with the exception of 8 amino acids. Slope of the steady-state Boltzmann voltage activation curve was 8.1 mV per e-fold change in probability of opening for both rbslo1 and delA. The apparent [Ca2+](i) properties in delA were more like mslo but the voltage-activation properties remained distinctly rbslo1. Ca2+ affinity decreased and transmembrane voltage effects on apparent Ca2+ affinity increased in delA. The differences between rbslo1 and other cloned channels appear to be localized at insertion site A with both the insertion sequence and amino acid substitutions near site A being important. The steeper activation slope makes the channel more responsive to small changes in transmembrane voltage while the insertion sequence makes the channel functional at physiological low levels of [Ca2+](i).

AB - We previously cloned a MaxiK channel α-subunit isoform, rbslo1, from rabbit kidney with an amino acid sequence highly homologous to mslo but with a 59 amino acid insertion between S8 and S9 (Morita et al., 1997. Am. J. Physiol. 273:F615-F624). rbslo1 activation properties differed substantially from mslo with much greater Ca2+ sensitivity, half-activation potential of -49 mV in 1 μM Ca2+. We now report single-channel analysis of rbslo1 and delA, a construct produced by removal of the 59 amino acid insertion at site A. delA is identical to mslo from upstream of S1 to downstream of S10 with the exception of 8 amino acids. Slope of the steady-state Boltzmann voltage activation curve was 8.1 mV per e-fold change in probability of opening for both rbslo1 and delA. The apparent [Ca2+](i) properties in delA were more like mslo but the voltage-activation properties remained distinctly rbslo1. Ca2+ affinity decreased and transmembrane voltage effects on apparent Ca2+ affinity increased in delA. The differences between rbslo1 and other cloned channels appear to be localized at insertion site A with both the insertion sequence and amino acid substitutions near site A being important. The steeper activation slope makes the channel more responsive to small changes in transmembrane voltage while the insertion sequence makes the channel functional at physiological low levels of [Ca2+](i).

KW - BK channel

KW - Gating

KW - Potassium channel

KW - Single-channel recording

UR - http://www.scopus.com/inward/record.url?scp=0032756398&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032756398&partnerID=8YFLogxK

U2 - 10.1007/s002329900596

DO - 10.1007/s002329900596

M3 - Article

VL - 172

SP - 193

EP - 201

JO - Journal of Membrane Biology

JF - Journal of Membrane Biology

SN - 0022-2631

IS - 3

ER -