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Biochemistry - Lecture 6 (15/02/2018)
Tertiary and Quaternary Structure
Loops and Turns
Loops and Turns connect α helices and β strands and allow a peptide chain to fold back on itself to form a compact structure.
Loops - Often contain hydrophilic residues and are found on protein surfaces.
Turns - Loops containing 5 residues or less.
Tertiary Structure of Globular Proteins
Tertiary structure = A closely packed three-dimensional form of a protein.
Each protein folds its polypeptide chain into a tertiary structure which is specifically adapted for a particular biological function.
Amino acids far apart in the primary structure can be brought together in a tertiary structure.
Amino acids distribute themselves so that non-polar side chains are found on the interior and polar/charged side chains are displayed on the exterior (not trans-membrane proteins).
Protein tertiary structures are stabilised primarily by non-covalent interactions between side chains. Disulfide bridges can also stabilise tertiary structure.
Myoglobin - (O2 binding molecule in Red Blood Cells)
Yellow = Non-polar.
Blue = Charged.
Turns: 4 x 3.6 = Around 14 Amino Acids.
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