Compare the Native & SDS PAGE gels to indicate if each sample is a monomer, dimer, trimer or tetramer.
a. Sample 1: ________________
b. Sample 2: ________________
c. Sample 3: ________________
d. Sample 4: ________________
“Protein X” has a molecular mass of 400 kDa when measured by size-exclusion chromatography. When subjected to SDS-PAGE, Protein X gives 3 bands with molecular masses of 180, 160, & 60 kDa. When SDS-PAGE is conducted a second time but in the presence of β-mercaptoethanol (β-ME), 3 bands form again, but this time with molecular masses of 160, 90, and 60 kDa. What is the subunit composition of Protein X? (Hint: draw both SDS-PAGE gels).