AAMC FL Practice Exam

What significant role does proline have in protein structure?

1. It strengthens peptide bonds

2. It breaks secondary structures

3. It connects subunits in quaternary structure

4. It stabilizes alpha/beta sheets

The correct answer is: It breaks secondary structures

Proline plays a unique and significant role in protein structure primarily due to its distinctive side chain, which contains a cyclic structure that can disrupt the regular backbone conformation of proteins. This characteristic allows proline to introduce bends or turns in the polypeptide chain, breaking the formation of secondary structures such as alpha helices and beta sheets. In essence, proline is often found in regions where a change in direction of the polypeptide is needed, contributing to the overall three-dimensional shape of proteins. Its presence can hinder the ability to form hydrogen bonds that are essential for the stability of alpha helices and beta sheets, thus facilitating the necessary flexibility within protein structures. This context is vital in understanding how proteins fold and function, highlighting proline's crucial role in maintaining the structural integrity and variability of protein architecture.