Single channel propetiers of the virus-encoded miniature potassium channel Kcv

Kcv is a potassium (K+) channel found in the genome of the virus PBCV-1 which infects the green unicellular alga Chlorella. Viral infection depends on Kcv activity. Blocking the channel prevents injection of viral DNA into the host cytoplasm and inhibits infection. Despite its miniature size (only 94 aa long), Kcv forms a functional channel in several heterologous systems and is therefore amenable for electrophysiological studies. Kcv is an excellent model for the pore of K+ channels. It forms a K+ selective and weakly voltage-dependent channel which is blocked by the well known K+ channel blocker barium. Basic properties of channels, such as permeability and gating, have been described so far only at the macroscopic level. In this poster we will present data on the single channel properties of Kcv, transiently expressed in Xenopus oocytes. Kcv has a single channel conductance of about 113 pS; its current-voltage relationship (I/V) has the shape of a tilted "S" and closely resembles the macrocurrent relationship. we will present evidence that the deviation from linearity is associated with an increase in fast flickering, which results in an increased single channel amplitude variance.