Protein Structure - Introductory Biology - Lecture Slides, Slides of Biology

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Protein Structure

• Protein structure is represented in a hierarchal scheme comprised of four levels: primary, secondary, tertiary and quaternary
• Primary structure
• The linear sequence of amino acids comprising a protein
• Secondary structure
• The regular repeating patterns of hydrogen-bonded backbone conformations
• Tertiary structure
• The packing of secondary structure elements to form a folded protein - Quaternary structure
• The relative arrangement of two or more individual polypeptide chains

Overview of Protein Structure

Secondary Structure

• Are structures formed due to hydrogen bonding between amino acids.
• The two most common secondary structures are alpha-helixes and pleated sheets.

Tertiary Structure

• The 3d conformation of a polypetide including the its lower level secondary structures.
• May involve covalent bonding in the form of disulfide bridges between cysteine amino acid residues.

Quaternary Structure

• The association of two or more polypeptides in 3d space.

Protein folding

• Protein folding is very complex, so complex even our most powerful computers are quite up to simulating it…yet.
• The final conformation is determined by the interaction between the amino acids and their environment.
• Amino acids can be polar, non-polar, charged, acidic or basic, hydrophobic or hydrophilic. These vary properties contribute to how the protein will fold.

Why is folding so hard to simulated

• The number of possible conformation increases exponentially as the polypeptide length increases.
• There are many interactions – with water, other amino acids within the polypeptide, with chaperone proteins that help proteins fold.
• When computing power increases it will be possible to simulate protein folding properly. This will allow us to design our own proteins.