What is the significance of the R-groups in fibrous proteins?

Fibrous proteins, like all proteins, are made of amino acids. Amino acids are composed of the following parts: a central carbon, and amino group, a carboxyl group, and an R-group. The R-group is what distinguishes one amino acid from the other. The R-groups in the fibrous proteins is also what provide the forces that maintain the proteins’ structures.

Examples of how R-groups may contribute to the shape of a protein are identified below.

• R-groups may contain polar hydrogens that result in hydrogen bonding within and between polypeptide chains. Similarly, two adjacent R-groups that each contain cysteine may form a disulfide bridge via oxidation.


• The R-groups may be hydrophobic or hydrophilic. The way in which these R-groups interact with their aqueous environments is a huge contributor in the shape that a protein becomes. Hydrophilic R-groups that have charged or polar R-groups tend to orient themselves outward, whereas hydrophobic R-groups tend to orient themselves inward.