Which protein helps to reduce water loss at the skin surface?

Keratin plays a crucial role in reducing water loss at the skin surface. It is a fibrous structural protein found in the outer layer of the skin, known as the epidermis. The presence of keratin helps to create a protective barrier that prevents transepidermal water loss, which is the process through which water evaporates from the body into the atmosphere. By contributing to the skin's waterproof qualities, keratin helps to maintain hydration levels within the body, making it essential for skin health and integrity.

Collagen, while also an important protein in skin structure, provides tensile strength and support to connective tissues but does not specifically contribute to water retention at the skin’s surface. Elastin is responsible for the elasticity of the skin, allowing it to stretch and recoil, but it does not serve a significant role in preventing water loss. Fibronectin is involved in cell adhesion and helps to organize the extracellular matrix but, like collagen and elastin, does not function primarily to reduce water loss from the skin. Thus, keratin is the key protein involved in minimizing water loss from the skin.