How chains adopt their three-dimensional shapes
Protein chains wind around in a 3-D arrangement that is dictated by the character of the amino acids. As the amino acids interact, they enforce this shaping of the chain. We call this process “protein folding”. The final shape that is adopted by the protein is generally very complicated. Protein scientists use specialized nomenclature to describe the resulting “protein fold”. Studies of how artificial proteins fold are helping in the discovery of folding rules and new synthetic folding arrangements that give us clues about how protein chains naturally fold.
- Protein chains often make abrupt turns called “hairpin turns”. Less abrupt turns are also common. Turns allow a protein to fold back upon itself so that we end up with something with a complicated three-dimensional shape.
- A few types of regular “secondary” structures crop up again and again (alpha helices, beta strands). Various sorts of weak interactions (such as hydrogen bonds) add up to help stabilize such secondary structures.
- Multiple chains can pack together to give “multimeric” proteins. A myoglobin molecule, for example, has but one chain. A single hemoglobin molecule has four. Fibrous proteins (keratin, silk and collagen, for example) are built of many many chains wound together in specialized registries.