Keratin

Keratin is a special kind of protein that gives strength and shape to many parts of animals. It is the main building block in things like hair, nails, feathers, horns, claws, and the outer layer of skin. This tough material helps protect animals from damage and stress.

Keratin does not dissolve in water or other common liquids, making it very durable. It forms strong bundles called intermediate filaments that give body parts like scales, hooves, and feathers their hardness and flexibility. Animals such as cattle, rhinos, and armadillos have extra layers of keratin that make their horns and shells even tougher.

There are two main types of keratin. One type is softer and found in all animals with backbones, while a harder type is only in reptiles and birds. This tough protein is one of the strongest natural materials in the world, similar in strength to another material called chitin.

Examples of occurrence

Alpha-keratins are found in all animals with backbones. They make up hair, including wool, the outer layer of skin, horns, nails, claws, and hooves of mammals, as well as the slime threads of hagfish. The baleen plates of filter-feeding whales are also made of keratin. Keratin filaments are found in skin cells in the outer layer of the skin. They are also present in many other cells that line surfaces in the body.

The harder beta-keratins are found only in reptiles and birds. They are found in the nails, scales, and claws of reptiles, in some reptile shells, and in the feathers, beaks, and claws of birds. These keratins are made mainly in a special way, but they can also be found in alpha-keratins. Recent studies show that sauropsid beta-keratins are quite different from alpha-keratins. The term corneous beta protein has been suggested to keep these two types clear.

Keratins are types of proteins that form long chains. They are found only in animals with backbones. Other animals, like roundworms, seem to have different kinds of proteins that help structure their cells.

Genes

The human body has special instructions called genes that make a type of protein called keratin. There are 54 of these genes, found in two groups on parts of the cells called chromosomes 12 and 17. This shows that these genes likely came from copying itself many times a long time ago.

The keratins include many different proteins, such as KRT23, KRT24, KRT25, KRT26, KRT27, KRT28, KRT31, KRT32, KRT33A, KRT33B, KRT34, KRT35, KRT36, KRT37, KRT38, KRT39, KRT40, KRT71, KRT72, KRT73, KRT74, KRT75, KRT76, KRT77, KRT78, KRT79, KRT8, KRT80, KRT81, KRT82, KRT83, KRT84, KRT85 and KRT86 that help make up hair, nails, and skin.

Protein structure

Scientists first learned about the sequences of keratins in the early 1980s. They found that there are two main types of keratins, called type I and type II. These keratins have a special structure with a central part made of four spiral shapes, separated by small links.

Keratin molecules twist together to form very strong structures. This strength comes from special bonds between parts of the keratin. Hair contains a lot of a special building block that helps create these strong bonds, which is why hair can smell when it burns.

Cornification

Cornification is the process that helps create a protective barrier in the skin's outer layers. During this process, cells make a lot of keratin, a tough protein that gives skin, hair, and nails their strength. As cells change and mature, they stop working and lose their nucleus and other parts, becoming filled almost entirely with keratin.

This makes the outer layer of the skin strong and almost waterproof. When we rub our hands or press on certain areas, the skin can become thicker, forming calluses that protect us. Keratin helps keep our skin, hair, and nails healthy by providing a strong, lasting structure.

Clinical significance

When keratin grows too much, it can cause skin problems like keratosis or hyperkeratosis. Changes in how keratin genes work can lead to several health issues, such as hair loss, skin blistering, and certain growths.

Some infections, like athlete's foot and ringworm, happen when fungi eat keratin. Keratin is tough and does not get broken down easily by stomach acids. Cats often swallow their own hair while cleaning themselves, which can create hairballs that they might cough up or pass in their waste. In very rare cases, people who eat their own hair can develop a serious stomach problem.

Keratin helps doctors learn about certain cancers. By looking at where keratin is found, doctors can figure out where a cancer started, even if it has spread to another part of the body.