Question

5. A native protein has a molecular weight of 150,000 Da. Denaturing SDS electrophoresis results in two bands with molecular weights of approximately 53,000 and 23,000 Da. What arrangement of polypeptide chains in the native protein would best explain these results?

Answer 1

5.) Given protein is a Tetramer, having two

53000 Da polypetide chains and two 23000 Da polypeptide chains.

Total protein size = 2 * 53,000 + 2* 23,000

= 152,000 Da

~ 150,000 Da (Native protein size)

SDS denatures the higher structures of the proteins leaving only primary structure .

2.) No , two proteins having same molecular weight need not to be same because though there molecular weight is coming out to be same by adding the total amino acids residues weight but the arrangement of amino acids within a polypeptide need not to be same, sequence of amino acids determines the folding of the polypetide chain and thus it's function.

No, proteins identity cannot be definitely assigned based on the molecular weight , two proteins can have same molecular weight but one can be cytosolic and other can be membrane protein, based on the sequence and type of amino acid residues.