What is the structural composition of α-keratin?

The structural composition of α-keratin is characterized by two α-helices twisted around each other, forming a coiled-coil structure. This arrangement is crucial for the strength and rigidity of the protein, which is found in various tissues, including hair, nails, and the outer layer of skin. The helical structure allows for the formation of fibrous and durable proteins that can withstand mechanical stress.

In the context of keratin, the coiled-coil configuration enables the formation of higher-order structures, such as fibers, which are essential for the protective function of keratin-rich tissues. The coiled-coil formation results from hydrophobic interactions between the helices, stabilizing the structure and contributing to its overall toughness.

This characteristic structure is distinct from the other options presented. Random coils of polypeptides would imply a lack of regular secondary structure, while extended β-sheets refer to a different type of protein folding found in beta-keratins, which are structurally different from the alpha-keratins. A mixture of loops and turns does not adequately describe the organized helical structure that is predominant in α-keratin. Therefore, the description of α-keratin as two α-helices twisted around each other best captures its