Determination of the molecular mass of the native β-cell sulfonylurea receptor
Skeer JM., Dégano P., Coles B., Potier M., Ashcroft FM., Ashcroft SJH.
In the present study we have determined the molecular mass of the β-cell sulfonylurea receptor in its native form by two different experimental approaches; gel filtration chromatography and radiation inactivation analysis. We first confirmed that the denatured photolabelled MIN6 β-cell receptor had a molecular size of 141 ± 2 kDa (mean ± S.E., n = 8). Under non-denaturing conditions, using gel filtration chromatography, apparent molecular masses of 166 ± 1 kDa (mean ± S.E., n = 3) and 182 ± 5 kDa (mean ± S.E., n = 4) were determined for the photoaffinity-labelled and unlabelled sulfonylurea receptor, respectively. We conclude that in the solubilized state the receptor exists as a monomer. Radiation inactivation analysis indicated that the receptor has a target size of 250 ± 30 kDa (mean ± S.E., n = 7). This value for the molecular mass is larger than that obtained from SDS-PAGE following photolabelling of the receptor (141 kDa) suggesting that the β-cell sulfonylurea receptor is composed of more than one subunit in the native membrane. © 1994.