Voltage-dependence of virus-encoded miniature K+ channel Kcv

S. Gazzarrini, J. L. Etten, D. DiFrancesco, G. Thiel, A. Moroni

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Kcv is a K+-selective channel encoded by the Paramecium bursaria Chlorella virus 1 (PBVC-1). Expression of this protein, so far the smallest known functional K+ channel, in Xenopus oocytes reveals an instantaneous and a time-dependent component during voltage-clamp steps. These two components have an identical sensitivity to the inhibitor amantadine, implying that they reflect distinct kinetic features of the same channel. About 70% of the channels are always open; at hyperpolarizing voltages the time-dependent channels (30%) open in a voltage-dependent manner reaching half-maximal activation at about -70 mV. At both extreme positive and negative voltages the open-channel conductance decreases in a voltage-dependent manner. To examine the mechanism underlying the voltage-dependence of Kcv we neutralized the two charged amino acids in the lipophilic N-terminus. However, this double mutation had no effect on the voltage-dependence of the channel, ruling against the possibility that these charged amino acids represent a membrane-embedded voltage sensor. We have considered whether a block by external divalent cations is involved in the voltage-dependence of the channel. The Kcv current was increased about 4-fold on reduction of external Ca2+ concentration by a factor of ten. This pronounced increase in current was observed on lowering Ca2+ but not Mg2+ and was voltage-independent. These data indicate a Ca2+-selective, but voltage-independent mechanism for regulation of channel conductance.

Original languageEnglish (US)
Pages (from-to)15-25
Number of pages11
JournalJournal of Membrane Biology
Volume187
Issue number1
DOIs
StatePublished - May 1 2002

Fingerprint

Paramecium
Viruses
Chlorella
Amino Acids
Amantadine
Divalent Cations
Xenopus
Oocytes
Mutation
Membranes
Proteins

Keywords

  • Ca block
  • K channel
  • Kcv
  • PBCV-1
  • Voltage-dependence

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

Cite this

Voltage-dependence of virus-encoded miniature K+ channel Kcv. / Gazzarrini, S.; Etten, J. L.; DiFrancesco, D.; Thiel, G.; Moroni, A.

In: Journal of Membrane Biology, Vol. 187, No. 1, 01.05.2002, p. 15-25.

Research output: Contribution to journalArticle

Gazzarrini, S. ; Etten, J. L. ; DiFrancesco, D. ; Thiel, G. ; Moroni, A. / Voltage-dependence of virus-encoded miniature K+ channel Kcv. In: Journal of Membrane Biology. 2002 ; Vol. 187, No. 1. pp. 15-25.
@article{c82384a74de64f7da766fdfa7134abbc,
title = "Voltage-dependence of virus-encoded miniature K+ channel Kcv",
abstract = "Kcv is a K+-selective channel encoded by the Paramecium bursaria Chlorella virus 1 (PBVC-1). Expression of this protein, so far the smallest known functional K+ channel, in Xenopus oocytes reveals an instantaneous and a time-dependent component during voltage-clamp steps. These two components have an identical sensitivity to the inhibitor amantadine, implying that they reflect distinct kinetic features of the same channel. About 70{\%} of the channels are always open; at hyperpolarizing voltages the time-dependent channels (30{\%}) open in a voltage-dependent manner reaching half-maximal activation at about -70 mV. At both extreme positive and negative voltages the open-channel conductance decreases in a voltage-dependent manner. To examine the mechanism underlying the voltage-dependence of Kcv we neutralized the two charged amino acids in the lipophilic N-terminus. However, this double mutation had no effect on the voltage-dependence of the channel, ruling against the possibility that these charged amino acids represent a membrane-embedded voltage sensor. We have considered whether a block by external divalent cations is involved in the voltage-dependence of the channel. The Kcv current was increased about 4-fold on reduction of external Ca2+ concentration by a factor of ten. This pronounced increase in current was observed on lowering Ca2+ but not Mg2+ and was voltage-independent. These data indicate a Ca2+-selective, but voltage-independent mechanism for regulation of channel conductance.",
keywords = "Ca block, K channel, Kcv, PBCV-1, Voltage-dependence",
author = "S. Gazzarrini and Etten, {J. L.} and D. DiFrancesco and G. Thiel and A. Moroni",
year = "2002",
month = "5",
day = "1",
doi = "10.1007/s00232-001-0147-5",
language = "English (US)",
volume = "187",
pages = "15--25",
journal = "Journal of Membrane Biology",
issn = "0022-2631",
publisher = "Springer New York",
number = "1",

}

TY - JOUR

T1 - Voltage-dependence of virus-encoded miniature K+ channel Kcv

AU - Gazzarrini, S.

AU - Etten, J. L.

AU - DiFrancesco, D.

AU - Thiel, G.

AU - Moroni, A.

PY - 2002/5/1

Y1 - 2002/5/1

N2 - Kcv is a K+-selective channel encoded by the Paramecium bursaria Chlorella virus 1 (PBVC-1). Expression of this protein, so far the smallest known functional K+ channel, in Xenopus oocytes reveals an instantaneous and a time-dependent component during voltage-clamp steps. These two components have an identical sensitivity to the inhibitor amantadine, implying that they reflect distinct kinetic features of the same channel. About 70% of the channels are always open; at hyperpolarizing voltages the time-dependent channels (30%) open in a voltage-dependent manner reaching half-maximal activation at about -70 mV. At both extreme positive and negative voltages the open-channel conductance decreases in a voltage-dependent manner. To examine the mechanism underlying the voltage-dependence of Kcv we neutralized the two charged amino acids in the lipophilic N-terminus. However, this double mutation had no effect on the voltage-dependence of the channel, ruling against the possibility that these charged amino acids represent a membrane-embedded voltage sensor. We have considered whether a block by external divalent cations is involved in the voltage-dependence of the channel. The Kcv current was increased about 4-fold on reduction of external Ca2+ concentration by a factor of ten. This pronounced increase in current was observed on lowering Ca2+ but not Mg2+ and was voltage-independent. These data indicate a Ca2+-selective, but voltage-independent mechanism for regulation of channel conductance.

AB - Kcv is a K+-selective channel encoded by the Paramecium bursaria Chlorella virus 1 (PBVC-1). Expression of this protein, so far the smallest known functional K+ channel, in Xenopus oocytes reveals an instantaneous and a time-dependent component during voltage-clamp steps. These two components have an identical sensitivity to the inhibitor amantadine, implying that they reflect distinct kinetic features of the same channel. About 70% of the channels are always open; at hyperpolarizing voltages the time-dependent channels (30%) open in a voltage-dependent manner reaching half-maximal activation at about -70 mV. At both extreme positive and negative voltages the open-channel conductance decreases in a voltage-dependent manner. To examine the mechanism underlying the voltage-dependence of Kcv we neutralized the two charged amino acids in the lipophilic N-terminus. However, this double mutation had no effect on the voltage-dependence of the channel, ruling against the possibility that these charged amino acids represent a membrane-embedded voltage sensor. We have considered whether a block by external divalent cations is involved in the voltage-dependence of the channel. The Kcv current was increased about 4-fold on reduction of external Ca2+ concentration by a factor of ten. This pronounced increase in current was observed on lowering Ca2+ but not Mg2+ and was voltage-independent. These data indicate a Ca2+-selective, but voltage-independent mechanism for regulation of channel conductance.

KW - Ca block

KW - K channel

KW - Kcv

KW - PBCV-1

KW - Voltage-dependence

UR - http://www.scopus.com/inward/record.url?scp=0036570608&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036570608&partnerID=8YFLogxK

U2 - 10.1007/s00232-001-0147-5

DO - 10.1007/s00232-001-0147-5

M3 - Article

C2 - 12029374

AN - SCOPUS:0036570608

VL - 187

SP - 15

EP - 25

JO - Journal of Membrane Biology

JF - Journal of Membrane Biology

SN - 0022-2631

IS - 1

ER -