Fibrous Protein Structure vs Globular Proteins

Fibrous Proteins Characteristics

• structural and mechanical roles

• long fibers/sheets

• repetitive sequences

• not soluble in aqueous solution

ex. of fibrous proteins

alpha keratin, collagen, fibron

alpha keratin geometry

two long alpha helices that make a rope (coiled coils)

Coiled coils geometry

Heptad repeat pattern: after 7 residues, the aa is repeated
a & d are nonpolar and form hydrophobic interactions
e & g are charged and form ionic interactions
b,c,f are charged or polar → exposed to solvents

Geometry of collagen

No alpha helices; instead, use three long polypeptide chains wrapped into a triple helix (left-handed). Form hydrogen bonds across different strands. staggered cross linked 3 helices.

Fibron structure

beta sheets for tensile strength and amorphous regions which are long lines for flexibility no defined