Protein E is a peptide hormone encoded by a gene encoding a protein with a mass

Question

Protein E is a peptide hormone encoded by a gene encoding a protein with a mass of 60 kDa. However, the active form of the hormone has a molecular weight of 120 kDa. The protein is enriched in alanine residues, and contains very few proline, glycine, and aromatic residues. Lastly, the active 120 kDa form cannot be isolated when DTT (a reducing agent) is present in the buffer. With this information, what can you deduce about likely structure of the protein in terms of the primary, secondary, tertiary, and quaternary structure based on the provided information

Explanation / Answer

Primary structure-

the structure is of a very long chain of amino acids

(since its weight is 60kDa)

Secondary structure-

The structure is that of alpha helix folding.

(as it is rich in alanine, which generally form alpha helixes)

Tertiary structure-

it contains thiol groups and folds upon itself and is connected by thiol groups.

(DTT is a protective agent for thiol groups and hence, protein cannot be isolated when DTT is present in buffer)

Quarternary structure-

It is functionally a dimer, ie one functional protein has 2 complete peptide chains.

(the functional molecular weight is twice (120kDa) as that of the primary structure weight)

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