Involvement of a novel C-terminal kinase domain of Kir6.2 in the K-ATP channel rundown reactivation

Rundown is a generally encountered problem while recording KATP channel activity with inside-out patches. No assigned structural fragment related to this mechanism has yet been derived from any of the functional analyses performed. Therefore, based on a combined sequence and secondary structure alignment against known crystal structure of segments from closely related proteins, we propose here the three-dimensional structural model of an intracellular C-terminal domain of the Kir6.2 subunit in KATP channels. An E. coli CMP-kinase was suggested as template for the model building. The subdomain arrangement of this novel kinase domain and the structural correlation for UDP-docking are described. With structural-functional interpretation, we conclude that the reactivation of KATP channel rundown by MgATP or UDP is very possibly regulated by this intracellular kinase domain at the C-terminus of Kir6.2 subunit in KATP channels.