Question

Most common secondary structure of protein Myosin in muscle and \(\alpha\)-keratin in hair are,

• A. both \(\alpha\)-helical
• B. \(\beta\)-pleated, \(\alpha\)-helical
• C. \(\alpha\)-helical, \(\beta\)-pleated
• D. both \(\beta\)-pleated

Hint:

Both are fibrous proteins whose chains coil into a right-handed helix held by hydrogen bonds.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Secondary structure of proteins is of two types: \(\alpha\)-helix and \(\beta\)-pleated sheet. Both are held by hydrogen bonds.

Step 2: Alpha-keratin
In \(\alpha\)-keratin of hair and wool the chain coils into a right-handed \(\alpha\)-helix. The C=O of one residue bonds to the N-H of the fourth residue along.

Step 3: Myosin
The long tail of myosin is also made of \(\alpha\)-helices wound round each other. The \(\beta\)-pleated sheet is typical of silk fibroin.

Final Answer:
Both myosin and alpha-keratin are alpha-helical. \[ \boxed{\text{(A) }\text{both }\alpha\text{-helical}} \]