KINETIC VARIABILITY AND MODULATION OF DSLO, A CLONED CALCIUM-DEPENDENT POTASSIUM CHANNEL

We have examined, using patch recording, the modulation by ATP gamma S of the cloned Drosophila slopoke calcium-dependent potassium channel (dslo) expressed in Xenopus oocytes. There is a large variation in the gating kinetics, open probability, and conductance level of the Chann el in this expression system, which complicates the analysis of modula tory events. Addition of ATP gamma S to the intracellular face of the patch does not consistently alter the overall open probability of dSlo , but it does increase the frequency of appearance of an exceptionally long-lived closed state of the channel. This modulation is not blocke d by an inhibitor of several serine/threonine protein kinases, nor by mutation of a serine residue that is a target for phosphorylation by p rotein kinase A. Thus, ATP gamma S may alter dSlo kinetic properties b y some mechanism other than serine/threonine phosphorylation. Copyrigh t (C) 1996 Elsevier Science Ltd