Regulation of Na+/K+ ATPase Transport Velocity by RNA Editing

Editing of Na+/K+ ATPase mRNAs modulates the Na+/K+ pump's turnover rate by selectively targeting the release of the final sodium to the outside

A ring of eight conserved negatively charged amino acids doubles the conductance of BK channels and prevents inward rectification

Large-conductance Ca(2+)–voltage-activated K(+) channels (BK channels) control many key physiological processes, such as neurotransmitter release and muscle contraction. A signature feature of BK channels is that they have the largest single channel conductance of all K(+) channels. Here we examine the mechanism of this large conductance. Comparison of the sequence of BK channels to lower-conductance K(+) channels and to a crystallized bacterial K(+) channel (MthK) revealed that BK channels have a ring of eight negatively charged glutamate residues at the entrance to the intracellular vestibule. This ring of charge, which is absent in lower-conductance K(+) channels, is shown to double the conductance of BK channels for outward currents by increasing the concentration of K(+) in the vestibule through an electrostatic mechanism. Removing the ring of charge converts BK channels to inwardly rectifying channels. Thus, a simple electrostatic mechanism contributes to the large conductance of BK channels