2 The molecular weight of an unspecified protein at physiolo

2. The molecular weight of an unspecified protein, at physiological conditions, is 7o,ooo Dalton, as 2. determined by gel-filtration chromatography. The sDs-polyacrylamide gel electrophoresis of the protein yields a single band corresponding to molecular weight of 7o,ooo Dalton. However, in the presence of the reducing agent, B- the SDS PAGE shows two bands, mercaptoethanol, corresponding to molecular weights of 30,000 and 20,000. a) From these data, describe the native protein in terms of the number of subunits present, their molecular weight, stoichiometry of subunits, and the kinds of bonding existing between each of the subunits. b) How would your answer to problem (a) change if the native molecular weight of the protein was 100,000 Dalton?

Solution

A. The native functional protein contain 3 subunits. One is with 30 kDa and, two with 20 k Da.

Sticometric ratio is 1:2 I.e one 30 kDa and two 20 kDa

The two subunits are linked by Disulphide Bonds (-S-S-).

3. If the protein molecular weight changes to 100 kDa, one more 30 kDa submit added to that 70 k Da protein