Biomaterial Database

Xenopus laevis oocytes contain endogenous large conductance Ca2(+)-activated K+ channels. 1996

J D Krause, and C D Foster, and P H Reinhart

Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.

Xenopus laevis oocytes have become a pre-eminent tool for studying cloned ion channels, primarily because they intrinsically express low levels of most types of ion channels. However, when these cells are used for single channel studies, it is essential to determine whether or not oocytes contain even low levels of endogenous ion channels with properties similar to the channel being investigated. We show here that X. laevis oocytes express endogenous large-conductance Ca2(+)-activated K+ channels with properties similar to mammalian isoforms of this channel. The endogenous channels exhibit a voltage-dependence of 12-14 mV per e-fold change in open probability (po), can be activated by micromolar Ca2+ concentrations, and have a single channel conductance of approximately 200 pS in symmetrical 110 mM K+ solutions. Patch clamp experiments indicate that this endogenous channel is present at low densities (approximately 1 channel/3000 microns2). If endogenous channel subunits can form functional tetramers with other exogenous potassium channel subunits, then they will give rise to the expression of a heterogeneous channel population. Therefore, studies involving the heterologous expression of large-conductance Ca2(+)-activated K+ channels in Xenopus laevis oocytes require careful analysis and interpretation.

UI	MeSH Term	Description	Entries
D009865	Oocytes	Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).	Ovocytes,Oocyte,Ovocyte
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014982	Xenopus laevis	The commonest and widest ranging species of the clawed "frog" (Xenopus) in Africa. This species is used extensively in research. There is now a significant population in California derived from escaped laboratory animals.	Platanna,X. laevis,Platannas,X. laevi
D015221	Potassium Channels	Cell membrane glycoproteins that are selectively permeable to potassium ions. At least eight major groups of K channels exist and they are made up of dozens of different subunits.	Ion Channels, Potassium,Ion Channel, Potassium,Potassium Channel,Potassium Ion Channels,Channel, Potassium,Channel, Potassium Ion,Channels, Potassium,Channels, Potassium Ion,Potassium Ion Channel
D051036	Large-Conductance Calcium-Activated Potassium Channels	A major class of calcium activated potassium channels whose members are voltage-dependent. MaxiK channels are activated by either membrane depolarization or an increase in intracellular Ca(2+). They are key regulators of calcium and electrical signaling in a variety of tissues.	BK Channel,Big K Channel,Large-Conductance Calcium-Activated Potassium Channel,Maxi K Channel,Maxi-K Channel,MaxiK Channel,BK Channels,Big K Channels,Maxi-K Channels,MaxiK Channels,Channel, BK,Channel, Big K,Channel, Maxi K,Channel, Maxi-K,Channel, MaxiK,K Channel, Big,K Channel, Maxi,Large Conductance Calcium Activated Potassium Channel,Large Conductance Calcium Activated Potassium Channels,Maxi K Channels
D018408	Patch-Clamp Techniques	An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.	Patch Clamp Technique,Patch-Clamp Technic,Patch-Clamp Technique,Voltage-Clamp Technic,Voltage-Clamp Technique,Voltage-Clamp Techniques,Whole-Cell Recording,Patch-Clamp Technics,Voltage-Clamp Technics,Clamp Technique, Patch,Clamp Techniques, Patch,Patch Clamp Technic,Patch Clamp Technics,Patch Clamp Techniques,Recording, Whole-Cell,Recordings, Whole-Cell,Technic, Patch-Clamp,Technic, Voltage-Clamp,Technics, Patch-Clamp,Technics, Voltage-Clamp,Technique, Patch Clamp,Technique, Patch-Clamp,Technique, Voltage-Clamp,Techniques, Patch Clamp,Techniques, Patch-Clamp,Techniques, Voltage-Clamp,Voltage Clamp Technic,Voltage Clamp Technics,Voltage Clamp Technique,Voltage Clamp Techniques,Whole Cell Recording,Whole-Cell Recordings
D024681	Potassium Channels, Calcium-Activated	Potassium channels whose activation is dependent on intracellular calcium concentrations.	Calcium-Activated Potassium Channels,Ca2+-Activated K+ Channels,Calcium-Activated Potassium Channel,Calcium-Dependent Potassium Channels,K+ Channels, Ca2+-Activated,K+ Channels, Calcium-Activated,Potassium Channel, Calcium-Activated,Potassium Channels, Calcium-Dependent,Ca2+ Activated K+ Channels,Calcium Activated Potassium Channel,Calcium Activated Potassium Channels,Calcium Dependent Potassium Channels,Calcium-Activated K+ Channels,Channels, Calcium-Dependent Potassium,K+ Channels, Ca2+ Activated,K+ Channels, Calcium Activated,Potassium Channel, Calcium Activated,Potassium Channels, Calcium Activated,Potassium Channels, Calcium Dependent