Which protein is an example of a tertiary structure?

Which protein is an example of a tertiary structure?

• A. Myoglobin
• B. Hemoglobin
• C. Collagen
• D. Keratin

Answer: (A)

Tertiary structure is the overall three-dimensional fold of a single polypeptide chain, stabilized by interactions among its side chains and any bound cofactors, forming a compact, globular shape. Myoglobin fits this description because it is a single polypeptide that folds into one compact globular domain with a heme-binding pocket, so its native conformation is defined by the tertiary arrangement of that one chain. Hemoglobin, by contrast, is made of multiple polypeptide chains that come together to form a tetramer, which is a quaternary structure. Collagen features three polypeptide chains that intertwine into a triple helix, a higher-order assembly beyond a single chain, and keratin also assembles into dimers and larger filaments through subunit interactions. So the best example of a tertiary structure is myoglobin.

Tertiary structure is the overall three-dimensional fold of a single polypeptide chain, stabilized by interactions among its side chains and any bound cofactors, forming a compact, globular shape. Myoglobin fits this description because it is a single polypeptide that folds into one compact globular domain with a heme-binding pocket, so its native conformation is defined by the tertiary arrangement of that one chain. Hemoglobin, by contrast, is made of multiple polypeptide chains that come together to form a tetramer, which is a quaternary structure. Collagen features three polypeptide chains that intertwine into a triple helix, a higher-order assembly beyond a single chain, and keratin also assembles into dimers and larger filaments through subunit interactions. So the best example of a tertiary structure is myoglobin.