secondary sturcture/supersecondary

SPEAKER 0

Super secondary structures are characteristic combinations of typical secondary structures like alpha helices and beta sheets. Here are key types:

1. Beta Alpha Beta Unit: Consists of parallel beta sheets connected by an alpha helix, resembling an "N" shape.

2. Alpha Alpha Unit: Features two anti-parallel alpha helices, also known as helix-turn-helix, shaped like a "U".

3. Beta Meander: Formed by anti-parallel beta sheets linked by tight reverse turns, creating a meandering pattern.

4. Greek Key: A structure where a polypeptide chain folds back on itself, resembling a maze.

Motifs are repetitive super secondary structures, which reveal protein folding but not function. A domain is a distinct section of a protein that folds and functions independently and can consist of multiple motifs.

Examples of Motifs include:

• Beta Barrel: A series of linked beta meanders, often serving as a transmembrane structure.

• Alpha Hemolysin: A pore-forming toxin shaped like a mushroom, released by Staphylococcus aureus, known for its role in staph infections.

• Collagen: Composed of three polypeptide chains in a triple helix, known for its strength and organized into water-insoluble fibers. It has a repeating sequence of amino acids and is cross-linked by covalent bonds with age.