Protein Structure Tutorials
Quaternary Structure: Protein Chains Combine to Make Protein Complexes
Secondary and tertiary structures are determined by a protein's sequence of amino acids, or primary structure. All proteins have primary, secondary and tertiary structure.
Some proteins are made up of more than one amino acid chain, giving them a quaternary structure. These multi-chain proteins are held together with the same forces as the tertiary structure of individual protein chains (hydrophobic, hydrophillic, positive/negative and cysteine interactions). Sometimes the various protein chains in a protein complex are identical and other times they are each unique.
Click on the proteins below to see their overall quaternary structure shown in the 3-dimensional display to the right. For each protein complex, the various chains have been colored differently.
A Review of Protein Structure
- Proteins are long chains of amino acids that fold into complex 3-dimensional shapes.
- Proteins come in an almost endless array of shapes and sizes, each type acting like a specialized molecular machine that performs a specific microscopic task.
- Primary Structure is the specific order of amino acids in a protein polypeptide chain. There are 20 different types of amino acids that can be incorporated into a protein chain, each with unique attributes (hydrophobic, hydrophillic, positive, negative, and cysteine).
- Secondary Structures are the alpha helices and beta pleated sheets present in a folded protein's structure.
- Tertiary Structure is the final shape of an entire amino acid chain. This shape is directly related to the function of the protein.
- Quaternary Structure exists when more than one amino acid chain comes together to form a protein complex.
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- MSOE Center for BioMolecular Modeling