Step 1: Recall protein types.
Proteins are either fibrous (tough, insoluble, structural) or globular (soluble, functional). Structural body parts like nails are made of fibrous proteins.
Step 2: Check Albumin.
Albumin is a soluble globular protein found in blood plasma, where it controls osmotic pressure - not a structural protein of nails.
Step 3: Check Keratin.
Keratin is a tough, insoluble fibrous protein that forms hair, nails and the outer skin layer in vertebrates. This fits a nail perfectly.
Step 4: Check Myosin.
Myosin is a motor protein in muscle that drives contraction, not a nail component.
Step 5: Check Legumelin.
Legumelin is a storage albumin found in legume seeds, unrelated to nails.
Step 6: Select the answer.
The fibrous structural protein of nails is keratin - option (2).
\[ \boxed{\text{Protein in nails: Keratin (option 2)}} \]