A protein was purified and then analyzed on a size exclusion

A protein was purified and then analyzed on a size exclusion column. Its MW was determined to be 130, 000 Dalton. The SDS-PAGE gel shows two bands, corresponding to molecular weights of 35, 000 and 20, 000 Dalton. Describe the native conformation of this protein in terms of the number of subunits present and their molecular weight.

Solution

Answer:

6. MW of the protein in size exclusion chromatography = 130 kDa

SDS-PAGE shows 2 bands at 35 kDa and 20 kDa. So, the protein should be composed of multiple subunits.

The most probable number of subunits present in the protein is 5.

35 kDa subunits = 2. So, molecular weight = 2 * 35 = 70 kDa

20 kDa subunits = 3. So, molecular weight = 3 * 20 = 60 kDa

Therefore, total molecular weight of all the subunits = (70 + 60) kDa = 130 kDa