A culture of insulin-responsive cells is analyzed after stimulation with insulin. The insulin receptors are then isolated (assum
e 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.
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.
