Fig. 2
Mapping of known properties of KATP to segments and structural features of SUR and KIR6.2. [See text for details (18)]. The -RKR- motif has been demonstrated to function as quality control (protein trafficking) signal in keeping incompletely assembled KATP (i.e. incorrect stoichiometry) from reaching the cell surface. This motif is found in the carboxy-terminus of subunit KIR6.2 and in sulfonylurea receptor protein for glibenclamide (SUR1) upstream of nucleotide-binding folds (NBF1), mutation of which leads to cell surface expression in the absence of the partner subunit (139). It may function as endoplasmic reticulum retention signal that is masked during assembly of the channel complex, thus, allowing only correctly assembled and functional (i.e. with regard to regulated conductivity) KATP to reach the plasma membrane. CHO, putative glycosylation sites. TMD, transmembrane domains.