Question

A culture of insulin-responsive cells is analyzed after stimulation with insulin. The insulin receptors are then isolated (assume that during the isolation protocol the insulin is removed from the receptor). Half of the sample is analyzed by SDS-PAGE followed by Coomassie blue staining. The other half of the sample is analyzed via SDS-PAGE followed by a Western blot. The primary antibody used in the blot recognizes phosphorylated tyrosine residues. Predict how many bands will be seen on the SDS-PAGE compared with the Western blot and explain your answer.

Answer 1

The α and β subunits of the insulin receptor form two bands in the SDS-PAGE gel. Moreover, in the Western blot analysis, there is just one band corresponding to the β subunit, since this subunit contains phosphorylated tyrosines, while α subunit doesn't have.