Determination of the molecular mass of the native β‐cell sulfonylurea receptor

Open Access
Publisher Website
Google Scholar
Abstract
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.