Figure 7.

Model for nucleotide activation of the K_ATP channel by SUR1 subunit. NBFs in the inactive state are depicted as circles; those with bound nucleotide and altered conformation are depicted as diamonds. State 1 is the active state in which SUR1 potentiates channel activity. States 2 and 3 are transient, and states 4 and 5 are inactive states in which SUR1 inhibits channel activity. The straight arrows indicate binding or unbinding reactions, and the wavy arrows indicate a hydrolytic reaction. The Mg²⁺ ion has been omitted for clarity. This model is modified from one in ref. 6.