Question

a protein composed of a single polypeptide has the following amino - acid sequence: met - ala - cys - his - ala - pro - met - ala - phe - cys. imagine you have an altered version of this protein that changes the first cysteine (cys) to a leucine (leu), as shown below: met - ala - leu - his - ala - pro - met - ala - phe - cys. review the structures of leucine and cysteine: structural formulas of leucine and cysteine. which levels of protein structure could be affected by changing the cysteine to a leucine in the altered polypeptide? quaternary structure only. primary structure only. both primary and tertiary structure. tertiary structure only.

Explanation:

The primary structure is the amino - acid sequence. Changing cysteine to leucine alters this sequence. Tertiary structure depends on interactions between R - groups. Cysteine has a sulfhydryl group which can form disulfide bridges, while leucine has a non - polar side chain. This change can affect tertiary structure. Since it's a single polypeptide, there's no quaternary structure.

Answer:

C. Both primary and tertiary structure