How do alpha keratin and beta keratin strengthen reptile skin?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

Reptile skin is strengthened by the presence of keratin, a protein that reinforces the cornified layer of the epidermis. These proteins function in two distinct ways to balance protection and flexibility:

Beta-keratin: This is a stiff material that provides structural rigidity and protection. In many reptiles, such as crocodiles and turtles, the outer surface of the scale consists exclusively of beta-keratin to create a durable, protective barrier.1
Alpha-keratin: This is a more pliable, flexible material. It is often found in the hinge regions of scales, allowing for movement. In lizards and snakes, alpha-keratin forms a continuous layer beneath the stiffer beta-keratin, providing a combination of strength and necessary elasticity.1

By utilizing these two types of keratin, reptiles are able to prevent desiccation—a critical adaptation for terrestrial life—while maintaining the physical integrity and mobility required for their specific modes of life.1