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Biology LibreTexts

Module 4: Protein Structure

  • Page ID
    24689
    • Module 4.1: Protein Structure
      The physical and chemical properties of the 20 different, naturally occurring amino acids dictate the shape of the protein and its interactions with its environment. Certain short sequences of amino acids in the protein also dictate where the protein resides in the cell. Proteins are composed of hundreds to thousands of amino acids. As you can imagine, protein folding is a complicated process and there are many potential shapes due to the large number of combinations of amino acids.
    • Module 4.2: Primary Structure
      A protein is composed of amino acids attached in a linear order. This basic level of protein structure is called it's primary structure and derives from the formation of peptide bonds between the individual amino acids. Each amino acid in the linear polymer is referred to as a residue. The order, or sequence of the amino acids is determined by information encoded in the cell's genes.
    • Module 4.3: Secondary Structure
      Before discussing secondary structure, it is important to appreciate the conformational plasticity of proteins. Each residue in a polypeptide has three bonds connecting mainchain atoms that are potentially free to rotate. The conformation of the atoms involved in these bonds describes the secondary structure of the protein. The rotation angle about a bond is referred to as a torsional angle. A torsional angle defines the relative orientation of four atoms in space and the angle between 2 planes.
    • Module 4.4: Tertiary Structure and Protein Stability
      Protein unfolding involves the conversion of the highly ordered native state (folded) state to a unfolded (denatured) state. During the unfolding process the primary structure (e.g. covalent bonds) of the protein does not change. The folded state usually has a single, well defined, and unique tertiary structure with a significant fraction of amino acids buried in the core of the protein, sequestered from the solvent. All amino acid sidechains will be exposed to the solvent in the unfolded state.