Electrokinetics of miniature K+ channel: open-state V sensitivity and inhibition by K+ driving force.
Kcv, isolated from a Chlorella virus, is the smallest known K+ channel. When Kcv is expressed in Xenopus oocytes and exposed to 50 mM: [K+](o), its open-state current-voltage relationship (I-V) has the shape of a "tilted S" between -200 and +120 mV. Details of this shape depend on the conditioning voltage (V (c)) immediately before an I-V recording. Unexpectedly, the I-V relationships, recorded in different [K+](o), do intersect. These characteristics are numerically described here by fits of a kinetic model to the experimental data. In this model, the V (c) sensitivity of I-V is mainly assigned to an affinity increase of external K+ association at more positive voltages. The general, tilted-S shape as well as the unexpected intersections of the I-V relationships are kinetically described by a decrease of the cord conductance by the electrochemical driving force for K+ in either direction, like in fast V-dependent blocking by competing ions.
Gazzarrini
Sabrina
S
Department of Biology and IBF-CNR, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy.
Abenavoli
Alessandra
A
Gradmann
Dietrich
D
Thiel
Gerhard
G
Moroni
Anna
A
D000818:Animals; D002708:Chlorella / Q000378:metabolism / Q000821:virology; D005260:Female; D015870:Gene Expression; D008564:Membrane Potentials / Q000502:physiology*; D008954:Models, Biological; D009865:Oocytes / Q000166:cytology; D017862:Phycodnaviridae / Q000235:genetics / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
C405463:Kcv potassium channel, Chlorella virus; D015221:Potassium Channels; D014764:Viral Proteins; D011188:Potassium