SUR2A is a member of the ABC transporter superfamily. SUR2A mediated regulation of KATP channels is essential as mutations in the nucleotide binding domains (NBDs) of SUR2A are associated with cardiovascular disorders. Studies of eukaryotic NBDs, such as SUR2A, are hindered by low solubility of the isolated domain. We hypothesized that the solubility of heterologously expressed SUR2A NBDs depends on the definition of the domain boundaries. Boundaries were initially predicted using a combination of a structure-based sequence alignment and homology modeling, and subsequently verified by testing the solubility of five SUR2A NBD1 constructs with different N- or C-terminal boundaries. The boundaries of SUR2A NBD1 essential for solubility were identified. CD and NMR data indicate that SUR2A NBD1 is folded. Our method may be applied as a general method for developing suitable constructs of other NBDs of ABC proteins such as SUR isoforms, SUR2B and SUR2C, and the vacuolar transporter, Ycf1p.

SUR2A is a member of the ABC transporter superfamily. SUR2A mediated regulation of KATP channels is essential as mutations in the nucleotide binding domains (NBDs) of SUR2A are associated with cardiovascular disorders. Studies of eukaryotic NBDs, such as SUR2A, are hindered by low solubility of the isolated domain. We hypothesized that the solubility of heterologously expressed SUR2A NBDs depends on the definition of the domain boundaries. Boundaries were initially predicted using a combination of a structure-based sequence alignment and homology modeling, and subsequently verified by testing the solubility of five SUR2A NBD1 constructs with different N- or C-terminal boundaries. The boundaries of SUR2A NBD1 essential for solubility were identified. CD and NMR data indicate that SUR2A NBD1 is folded. Our method may be applied as a general method for developing suitable constructs of other NBDs of ABC proteins such as SUR isoforms, SUR2B and SUR2C, and the vacuolar transporter, Ycf1p.

Hair disorders cause psychological distress but are generally poorly controlled; more effective treatments are required. Despite the long-standing use of minoxidil for balding, its mechanism is unclear; suggestions include action on vasculature or follicle cells. Similar drugs also stimulate hair, implicating ATP-sensitive potassium (K(ATP)) channels. To investigate whether K(ATP) channels are present in human follicles, we used organ culture, molecular biological, and immunohistological approaches. Minoxidil and tolbutamide, a K(ATP) channel blocker, opposed each other's effects on the growing phase (anagen) of scalp follicles cultured in media with and without insulin. Reverse transcriptase-polymerase chain reaction identified K(ATP) channel component gene expression including regulatory sulfonylurea receptors (SUR) SUR1 and SUR2B but not SUR2A and pore-forming subunits (Kir) Kir6.1 and Kir6.2. When hair bulb tissues were examined separately, epithelial matrix expressed SUR1 and Kir6.2, whereas both dermal papilla and sheath exhibited SUR2B and Kir6.1. Immunohistochemistry demonstrated similar protein distributions. Thus, human follicles respond biologically to K(ATP) channel regulators in culture and express genes and proteins for two K(ATP) channels, Kir6.2/SUR1 and Kir6.1/SUR2B; minoxidil only stimulates SUR2 channels. These findings indicate that human follicular dermal papillae contain K(ATP) channels that can respond to minoxidil and that tolbutamide may suppress hair growth clinically; novel drugs designed specifically for these channels could treat hair disorders.