What describes the 'core' of protein-protein interfaces?

The core of protein-protein interfaces is primarily hydrophobic and located internally. This characteristic is essential for the stability of protein-protein interactions, as hydrophobic residues tend to be buried away from the aqueous environment, minimizing their exposure to water. When two proteins interact, the burial of hydrophobic side chains helps to drive the association of the proteins together, largely due to the unfavorable nature of water interacting with nonpolar groups.

The internal location of these hydrophobic regions assists in creating a robust and stable interface, crucial for the overall functionality of protein complexes. The hydrophobic effect plays a significant role in the folding and stability of proteins, thus making the core of protein-protein interfaces predominantly hydrophobic in nature. This arrangement also ensures that polar or ionic interactions can occur at the surface of the interface, where they contribute to additional specificity and stability without disrupting the hydrophobic core.